Building Browsergames » code http://buildingbrowsergames.com Ever wanted to build a browsergame? Mon, 29 Mar 2010 14:00:39 +0000 http://wordpress.org/?v=2.8.5 en hourly 1 Implementing Multiple Areas (Perl) http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/ http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/#comments Mon, 19 Jan 2009 14:00:58 +0000 Luke http://buildingbrowsergames.com/?p=689 Now that our database is prepared for multiple areas, we are going to build multiple areas into our exploration/combat system.

To start off, check out version 47 of our code from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/php/pbbg tutorial -r 47

With a fresh checkout of the code, we can get started. The first thing we will do is copy the code from forest.cgi over to explore.cgi, which is where we will now be storing our exploration code. Once that’s done, we will need to change the way that our script retrieves the current monster for a player to fight:

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my $area_id = $query->url_param('area');
$sth = $dbh->prepare("SELECT monster FROM area_monsters WHERE area = ? ORDER BY RAND() LIMIT 1");
$sth->execute($area_id);
my $monster_id;
$sth->bind_columns(\$monster_id);
$sth->fetch;
$sth = $dbh->prepare("SELECT name FROM monsters WHERE id = ?");
$sth->execute($monster_id);
$sth->bind_columns(\$parameters{monster});
$sth->fetch;

Because we will be intermingling arguments passed through both GET and POST for our code, we have to use the url_param method – we will also need to make a slight change to how we determine whether we’re being POST’d to or not:

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if($query->request_method() eq 'POST') {

With our code changes made, we need to put areas and monsters in areas into our database for our code to retrieve:

INSERT INTO areas(name) VALUES ('Forest');
INSERT INTO areas(name) VALUES ('Woods');
INSERT INTO area_monsters(area,monster) VALUES (1,1);
INSERT INTO area_monsters(area,monster) VALUES (1,2);
INSERT INTO area_monsters(area,monster) VALUES (2,3);

Once the data is inserted, our changes are (mostly) complete. Try visiting explore.cgi?area=1, and refreshing a few times – you should only ever see monsters appearing that belong in the area with the ID of 1.

While you are testing that, you may have noticed that the title tag for our page still says ‘The Forest’ – we should probably modify our code to also retrieve the name of the area we’re visiting:

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my $area_id = $arguments{'area'};
$sth = $dbh->prepare("SELECT name FROM areas WHERE id = ?");
$sth->execute($area_id);
$sth->bind_columns(\$parameters{area_name});
$sth->fetch;
 
my $template = HTML::Template->new(
		filename	=>	'explore.tmpl',

With that code added, it’s easy enough to tweak our template(renamed from forest.tmpl to explore.tmpl) to display the current area in it’s <title> tag, in addition to changing where our combat form POSTs to:

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    	<title>The <!--tmpl_var name='area_name'--></title>
    </head>
    <body>
    	<tmpl_unless name='combat'>
    		<p>You've encountered a <!--tmpl_var name='monster'-->!</p>
    		<form action='explore.cgi?area=<!--tmpl_var name='area'-->' method='post'>
    			<input type='submit' name='action' value='Attack' /> or 
    			<input type='submit' name='action' value='Run Away' />
    			<input type='hidden' name='monster' value='<!--tmpl_var name='monster'-->' />
    		</form>
    	<tmpl_else>
    		<ul>
    		<tmpl_loop name='combat'>
    			<li><strong><!--tmpl_var name='attacker'--></strong> attacks <!--tmpl_var name='defender'--> for <!--tmpl_var name='damage'--> damage!</li>
    		</tmpl_loop>
    		</ul>
    		<tmpl_if name='won'>
    			<p>You killed <strong><!--tmpl_var name='monster'--></strong>! You gained <strong><!--tmpl_var name='gold'--></strong> gold, and <strong><!--tmpl_var name='exp'--></strong> experience.</p>
    			<tmpl_if name='level_up'>
        			<p><strong>You gained a level!</strong></p>
    			</tmpl_if>
    			<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>
    			<p><a href='explore.cgi?area=<!--tmpl_var name='area'-->'>Explore Again</a></p>

With our template changes finished, we’re done! Your game can now support multiple different areas that players can encounter enemies in – all you have to do is link them to explore.cgi?area=<area_id>, where <area_id> is an ID for an area in the database. Here’s what our new code looks like:

explore.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(warningsToBrowser fatalsToBrowser);
use Data::Dumper;
use HTML::Template;
use DBI;
use config;
use weaponstats;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
if($query->request_method() eq 'POST') {
	if($arguments{action} eq 'Attack') {
		# fighting the monster	
		use stats;
		use monsterstats;
		my $cookie = $query->cookie('username+password'); 
		my ($username) = split(/\+/,$cookie);
		$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
		$sth->execute($username);
		my $userID;
		$sth->bind_columns(\$userID);
		$sth->fetch;
		my %player = (
			name		=>	$username,
			attack		=>	stats::getStat('atk',$userID),
			defence		=>	stats::getStat('def',$userID),
			curhp		=>	stats::getStat('curhp',$userID)
		);
		my $phand = stats::getStat('phand',$userID);
		$player{attack} += weaponstats::getWeaponStat('atk',$phand);
		use armorstats;
		my @armor = qw(atorso ahead alegs aright aleft);
		foreach my $key(@armor) {
			my $id = stats::getStat($key,$userID);
			my $defence = armorstats::getArmorStat('defence',$id);
			$player{defence} += $defence;
		}		
		$sth = $dbh->prepare("SELECT id FROM monsters WHERE name = ?");
		$sth->execute($arguments{monster});
		my $monsterID;
		$sth->bind_columns(\$monsterID);
		$sth->fetch;
		my %monster = (
			name		=>	$arguments{monster},
			attack		=>	monsterstats::getMonsterStat('atk',$monsterID),
			defence		=>	monsterstats::getMonsterStat('def',$monsterID),
			curhp		=>	monsterstats::getMonsterStat('maxhp',$monsterID)
		);
		my @combat;
		my $turns = 0;
		my ($attacker,$defender);
		while($player{curhp} > 0 && $monster{curhp} > 0) {
			my %attack;
			if($turns % 2 != 0) {
				$attacker = \%monster;
				$defender = \%player;
			} else {
				$attacker = \%player;
				$defender = \%monster;
			}
			my $damage = 0;
			if($attacker->{attack} > $defender->{defence}) {
				$damage = $attacker->{attack} - $defender->{defence};	
			}
			my %attack = (
				attacker => $attacker->{name},
				defender => $defender->{name},
				damage => $damage
			);
			$defender->{curhp} -= $damage;
			push @combat, \%attack;
			$turns++;
		}
		stats::setStat('curhp',$userID,$player{curhp});
		if($player{curhp} > 0) {
			# player won
			stats::setStat('gc',$userID,stats::getStat('gc',$userID) + monsterstats::getMonsterStat('gc',$monsterID));
			$parameters{won} = 1;
			$parameters{gold} = monsterstats::getMonsterStat('gc',$monsterID);
			my $rand = int(rand(99))+1;
			$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
			$sth->execute($monsterID,$rand);
			my $itemID;
			$sth->bind_columns(\$itemID);
			$sth->fetch;
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
			$sth->execute($itemID);
			$sth->bind_columns(\$parameters{item});
			$sth->fetch;
 
            my $monster_exp = monsterstats::getMonsterStat('exp',$monsterID);
            $parameters{exp} = $monster_exp;
            my $exp_rem = stats::getStat('exp_rem',$userID);
            $exp_rem -= $monster_exp;
            if($exp_rem <= 0) {
                $exp_rem = 100;
                $parameters{level_up} = 1;
            }
            stats::setStat('exp_rem',$userID,$exp_rem);   		
		} else {
			# monster won	
			$parameters{lost} = 1;
		}
		$parameters{combat} = \@combat;
	} else {
		# running away - back to the index page!
		print $query->redirect('index.cgi');
	}	
} else {
    my $area_id = $arguments{'area'};
    $sth = $dbh->prepare("SELECT monster FROM area_monsters WHERE area = ? ORDER BY RAND() LIMIT 1");
    $sth->execute($area_id);
    my $monster_id;
    $sth->bind_columns(\$monster_id);
    $sth->fetch;
    $sth = $dbh->prepare("SELECT name FROM monsters WHERE id = ?");
    $sth->execute($monster_id);
    $sth->bind_columns(\$parameters{monster});
    $sth->fetch;
}
 
my $area_id = $query->url_param('area');
$sth = $dbh->prepare("SELECT name FROM areas WHERE id = ?");
$sth->execute($area_id);
$sth->bind_columns(\$parameters{area_name});
$sth->fetch;
 
my $template = HTML::Template->new(
		filename	=>	'explore.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

explore.tmpl:

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<html>
<head>
	<title>The <!--tmpl_var name='area_name'--></title>
</head>
<body>
	<tmpl_unless name='combat'>
		<p>You've encountered a <!--tmpl_var name='monster'-->!</p>
		<form action='explore.cgi?area=<!--tmpl_var name='area'-->' method='post'>
			<input type='submit' name='action' value='Attack' /> or 
			<input type='submit' name='action' value='Run Away' />
			<input type='hidden' name='monster' value='<!--tmpl_var name='monster'-->' />
		</form>
	<tmpl_else>
		<ul>
		<tmpl_loop name='combat'>
			<li><strong><!--tmpl_var name='attacker'--></strong> attacks <!--tmpl_var name='defender'--> for <!--tmpl_var name='damage'--> damage!</li>
		</tmpl_loop>
		</ul>
		<tmpl_if name='won'>
			<p>You killed <strong><!--tmpl_var name='monster'--></strong>! You gained <strong><!--tmpl_var name='gold'--></strong> gold, and <strong><!--tmpl_var name='exp'--></strong> experience.</p>
			<tmpl_if name='level_up'>
    			<p><strong>You gained a level!</strong></p>
			</tmpl_if>
			<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>
			<p><a href='explore.cgi?area=<!--tmpl_var name='area'-->'>Explore Again</a></p>
		</tmpl_if>
		<tmpl_if name='lost'>
			<p>You were killed by <strong><!--tmpl_var name='monster'--></strong>.</p>
		</tmpl_if>
		<p><a href='index.cgi'>Back to main</a></p>
	</tmpl_unless>
</body>
</html>

Extra Credit

  • Make the explore page verify that the area ID passed to explore.cgi actaully exists within the database(hint: SELECT COUNT).
]]> http://buildingbrowsergames.com/2009/01/19/implementing-multiple-areas-perl/feed/ 0 Implementing Multiple Areas (PHP) http://buildingbrowsergames.com/2009/01/15/implementing-multiple-areas-php/ http://buildingbrowsergames.com/2009/01/15/implementing-multiple-areas-php/#comments Thu, 15 Jan 2009 14:00:11 +0000 Luke http://buildingbrowsergames.com/?p=686 Now that we’ve prepared our database for multiple areas, it’s time to build multiple area support into our exploration/combat system.

To begin with, check out version 46 from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/php/pbbg tutorial -r 46

With that done, we can get down to business. Start by copying all of forest.php’s code over to explore.php, which is going to be the new location of our exploration code. Once that’s done, we need to change the way that our script retrieves the current monster for a player to fight:

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$area_id = $_GET['area'];
$query = sprintf("SELECT monster FROM area_monsters WHERE area = %s ORDER BY RAND() LIMIT 1",
    mysql_real_escape_string($area_id));
$result = mysql_query($query);
list($monster_id) = mysql_fetch_row($result);
$query = sprintf("SELECT name FROM monsters WHERE id = %s",
    mysql_real_escape_string($monster_id));
$result = mysql_query($query);
list($monster) = mysql_fetch_row($result);
$smarty->assign('monster',$monster);

Note: this code should overwrite your old code, starting at line 129. We are modifying the way that monster retrieval works.

With the code changes made, we should set up areas and monsters in areas for our code to retrieve:

INSERT INTO areas(name) VALUES ('Forest');
INSERT INTO areas(name) VALUES ('Woods');
INSERT INTO area_monsters(area,monster) VALUES (1,1);
INSERT INTO area_monsters(area,monster) VALUES (1,2);
INSERT INTO area_monsters(area,monster) VALUES (2,3);

With the new data inserted, try visiting explore.php?area=1, and see what happens – you should only ever see monsters that belong in the area with the ID of 1.

While you’re testing, you might notice that the title tag of our page still says ‘The Forest’ – while we’re at it, we may as well modify our code to also retrieve the name of the area we are currently visiting:

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$query = sprintf("SELECT name FROM areas WHERE id = %s",
    mysql_real_escape_string($_GET['area']));
$result = mysql_query($query);
list($area_name) = mysql_fetch_row($result);
$smarty->assign('area',$area_name);
$smarty->assign('area_id',$_GET['area']);
 
$smarty->display('explore.tpl');

That code should be outside any of the code responding to whether our page is being POST’d to or not; we need to set the page title properly whether we’re just encountering something, or completing a fight. You’ll notice that we have also set the area_id – this is because we will need to tweak where the form in our template goes, in addition to renaming it from forest.tpl to explore.tpl:

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	<title>The {$area}</title>
</head>
<body>
	{if $combat eq ''}
		<p>You've encountered a {$monster}!</p>
		<form action='explore.php?area={$area_id}' method='post'>
			<input type='submit' name='action' value='Attack' /> or 
			<input type='submit' name='action' value='Run Away' />
			<input type='hidden' name='monster' value='{$monster}' />
		</form>
	{else}
		<ul>
		{foreach from=$combat key=id item=i}
			<li><strong>{$i.attacker}</strong> attacks {$i.defender} for {$i.damage} damage!</li>
		{/foreach}
		</ul>
		{if $won eq 1}
			<p>You killed <strong>{$smarty.post.monster}</strong>! You gained <strong>{$gold}</strong> gold, and {$exp} experience.</p>
			{if $level_up eq 1}
			    <p><strong>You gained a level!</strong></p>
			{/if}
			<p>You found a <strong>{$item}</strong>!</p>
			<p><a href='explore.php?area={$area_id}'>Explore Again</a></p>

With those changes made, we’re finished! Your game can now support multiple different areas where players can encounter enemies – just link them to explore.php?area=1 for area 1, explore.php?area=2 for area 2, and so on. Here’s what our new code files look like:

explore.php:

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<?php
 
require_once 'smarty.php';
require_once 'weapon-stats.php';
require_once 'login-check.php';
 
session_start();
 
require_once 'config.php';		// our database settings
$conn = mysql_connect($dbhost,$dbuser,$dbpass)
	or die('Error connecting to mysql');
mysql_select_db($dbname);
 
if($_POST) {
	if($_POST['action'] == 'Attack') {
		require_once 'stats.php';			// player stats
		require_once 'monster-stats.php';	// monster stats
		// to begin with, we'll retrieve our player and our monster stats 
		$query = sprintf("SELECT id FROM users WHERE UPPER(username) = UPPER('%s')",
					mysql_real_escape_string($_SESSION['username']));
		$result = mysql_query($query);
		list($userID) = mysql_fetch_row($result);
		$player = array (
			name		=>	$_SESSION['username'],
			attack 		=>	getStat('atk',$userID),
			defence		=>	getStat('def',$userID),
			curhp		=>	getStat('curhp',$userID)
		);
		$phand = getStat('phand',$userID);
		$atk = getWeaponStat('atk',$phand);
		$player['attack'] += $atk;
		require_once 'armor-stats.php';		// armor stats
		$armor = array('atorso','ahead','alegs','aright','aleft');
		foreach ($armor as $key) {
			$id = getStat($key,$userID);
			$defence = getArmorStat('defence',$id);
			$player['defence'] += $defence;
		}		
 
		$query = sprintf("SELECT id FROM monsters WHERE name = '%s'",
					mysql_real_escape_string($_POST['monster']));
		$result = mysql_query($query);
		list($monsterID) = mysql_fetch_row($result);
		$monster = array (
			name		=>	$_POST['monster'],
			attack		=>	getMonsterStat('atk',$monsterID),
			defence		=>	getMonsterStat('def',$monsterID),
			curhp		=>	getMonsterStat('maxhp',$monsterID)
		);
		$combat = array();
		$turns = 0;		
		while($player['curhp'] > 0 && $monster['curhp'] > 0 && $turns <= 100) {
			if($turns % 2 != 0) {
				$attacker = &$monster;
				$defender = &$player;	
			} else {
				$attacker = &$player;
				$defender = &$monster;
			}
			$damage = 0;
			if($attacker['attack'] > $defender['defence']) {
				$damage = $attacker['attack'] - $defender['defence'];	
			}
			$defender['curhp'] -= $damage;
			$combat[$turns] = array(
				attacker	=>	$attacker['name'],
				defender	=>	$defender['name'],
				damage		=>	$damage
			);
			$turns++;
		}
		setStat('curhp',$userID,$player['curhp']);
		if($player['curhp'] > 0) {
			// player won
			setStat('gc',$userID,getStat('gc',$userID)+getMonsterStat('gc',$monsterID));	
			$smarty->assign('won',1);
			$smarty->assign('gold',getMonsterStat('gc',$monsterID));
			$rand = rand(0,100);
			$query = sprintf("SELECT item_id FROM monster_items WHERE monster_id = %s AND rarity >= %s ORDER BY RAND() LIMIT 1",
				mysql_real_escape_string($monsterID),
				mysql_real_escape_string($rand));
			$result = mysql_query($query);
			list($itemID) = mysql_fetch_row($result);
			$query = sprintf("SELECT count(id) FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
				mysql_real_escape_string($userID),mysql_real_escape_string($itemID));
			$result = mysql_query($query);
			list($count) = mysql_fetch_row($result);
			if ($count > 0) {
				# already has one of the item
				$query = sprintf("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = '%s' AND item_id = '%s'",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			} else {
				# has none - new row
				$query = sprintf("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,'%s','%s')",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			}
			mysql_query($query);
			# retrieve the item name, so that we can display it
			$query = sprintf("SELECT name FROM items WHERE id = %s",
				mysql_real_escape_string($itemID));
			$result = mysql_query($query);
			list($itemName) = mysql_fetch_row($result);
			$smarty->assign('item',$itemName);
 
			$monster_exp = getMonsterStat('exp',$monsterID);
			$smarty->assign('exp',$monster_exp);
			$exp_rem = getStat('exp_rem',$userID);
			$exp_rem -= $monster_exp;
			$level_up = 0;
			if($exp_rem <= 0) {
			    // level up!
			    $exp_rem = 100;
			    $level_up = 1;
			}
		    $smarty->assign('level_up',$level_up);
			setStat('exp_rem',$userID,$exp_rem);
		} else {
			// monster won
			$smarty->assign('lost',1);	
		}
		$smarty->assign('combat',$combat);
	} else {
		// Running away! Send them back to the main page
		header('Location: index.php');	
	}
} else {
    $area_id = $_GET['area'];
    $query = sprintf("SELECT monster FROM area_monsters WHERE area = %s ORDER BY RAND() LIMIT 1",
        mysql_real_escape_string($area_id));
    $result = mysql_query($query);
    list($monster_id) = mysql_fetch_row($result);
    $query = sprintf("SELECT name FROM monsters WHERE id = %s",
        mysql_real_escape_string($monster_id));
    $result = mysql_query($query);
    list($monster) = mysql_fetch_row($result);
    $smarty->assign('monster',$monster);
}
 
$query = sprintf("SELECT name FROM areas WHERE id = %s",
    mysql_real_escape_string($_GET['area']));
$result = mysql_query($query);
list($area_name) = mysql_fetch_row($result);
$smarty->assign('area',$area_name);
$smarty->assign('area_id',$_GET['area']);
 
$smarty->display('explore.tpl');
 
?>

explore.tpl:

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<html>
<head>
	<title>The {$area}</title>
</head>
<body>
	{if $combat eq ''}
		<p>You've encountered a {$monster}!</p>
		<form action='explore.php?area={$area_id}' method='post'>
			<input type='submit' name='action' value='Attack' /> or 
			<input type='submit' name='action' value='Run Away' />
			<input type='hidden' name='monster' value='{$monster}' />
		</form>
	{else}
		<ul>
		{foreach from=$combat key=id item=i}
			<li><strong>{$i.attacker}</strong> attacks {$i.defender} for {$i.damage} damage!</li>
		{/foreach}
		</ul>
		{if $won eq 1}
			<p>You killed <strong>{$smarty.post.monster}</strong>! You gained <strong>{$gold}</strong> gold, and {$exp} experience.</p>
			{if $level_up eq 1}
			    <p><strong>You gained a level!</strong></p>
			{/if}
			<p>You found a <strong>{$item}</strong>!</p>
			<p><a href='explore.php?area={$area_id}'>Explore Again</a></p>
		{/if}
		{if $lost eq 1}
			<p>You were killed by <strong>{$smarty.post.monster}</strong>.</p>
		{/if}		
			<p><a href='index.php'>Back to main</a></p>
	{/if}
</body>
</html>

Extra Credit

  • Make it so that when the user visits explore.php without passing in an area to visit, a random area is selected for them to explore.
]]> http://buildingbrowsergames.com/2009/01/15/implementing-multiple-areas-php/feed/ 0 How to install libraries for yourself if your host won’t http://buildingbrowsergames.com/2008/11/20/how-to-install-libraries-for-yourself-if-your-host-wont/ http://buildingbrowsergames.com/2008/11/20/how-to-install-libraries-for-yourself-if-your-host-wont/#comments Thu, 20 Nov 2008 14:00:58 +0000 Luke http://buildingbrowsergames.com/?p=543 If you are working on building your own browsergame, you may not want to shell out the cash for an actual hosting package straight away – preferring instead to work with free hosting until your game is a little closer to completion.

However, one of the downsides to using a free hosting service is that typically there isn’t a support team – or if there is, they are unwilling or unable to install extra modules for you as neccessary. In that sort of situation, you are left installing things like Smarty or HTML::Template on your own.

Thankfully, this is actually a fairly simple process. First, you need to download the code for whichever library you would like to install. Then, you need to upload the library’s source code to a location on your language’s path. The path varies from system to system – this will tell you what it is:

PHP:

<?php
 phpinfo();
?>

Perl:

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#!/usr/bin/perl -w
 
use CGI qw(:cgi);
my $q = new CGI;
print $q->header();
foreach my $dir(@INC) {
	print "$dir<br />";
}

Save whichever piece of code is applicable to you into a file on your server, and then navigate to it – the PHP file will display as much information about your environment as it can, and the Perl script will display the contents of @INC(which is Perl’s include path). In the PHP case, you need to find the variable ‘include_path’ – it’s value will tell you which directories are searched for library code when a PHP file is executed. In Perl’s case, each of the directories listed in @INC is a location that will be searched.

If you do not have access to any of the locations on your path, you can easily modify your path to include locations you do have access to – using PHP’s set_include_path, and Perl’s lib module. Here’s how you’d modify your path in either language:

PHP:

<?php
	set_include_path('/your/home/directory/lib');
	# your code goes here!
?>

Perl:

#!/usr/bin/perl -w
 
use lib '/your/home/directory/lib';
# your code goes here!

If you aren’t sure where your home directory is, you can easily figure that out too:

PHP:

<?php
echo $_SERVER['DOCUMENT_ROOT'];
?>

Perl:

#!/usr/bin/perl -w
 
use CGI qw(:cgi);
my $q = new CGI;
print $q->header();
print $ENV{DOCUMENT_ROOT};

The DOCUMENT_ROOT environment variable will give you the absolute path to the location where all of the files visible to the internet from your hosting account live. You can use that value to determine exactly where you should put your files – although I recommend putting them in a /lib directory directly underneath your DOCUMENT_ROOT.

It should be noted here that you could dynamically modify your path(because DOCUMENT_ROOT is an environment variable, after all) – however, this is not recommended. That’s because if you are dynamically modifying your DOCUMENT_ROOT and it changes for whatever reason, all of your includes are now broken – so most people make it easier for themselves by simply hard-coding the path to their extra libraries.

This method for adding modules and packages yourself doesn’t have to only be used for Smarty or HTML::Template, also – you can use it to install any extra libraries that you need.

]]> http://buildingbrowsergames.com/2008/11/20/how-to-install-libraries-for-yourself-if-your-host-wont/feed/ 1 Rawrmy’s Inventory http://buildingbrowsergames.com/2008/11/03/rawrmys-inventory/ http://buildingbrowsergames.com/2008/11/03/rawrmys-inventory/#comments Mon, 03 Nov 2008 14:00:29 +0000 Luke http://buildingbrowsergames.com/?p=538 This week, I focused on developing Rawrmy’s inventory system.

The typical inventory system is fairly simple: you have the player who owns the item, the item itself, and (perhaps) the quantity of the item.

One of the nicer features of Django that building the inventory system has introduced me to is reverse relations; they make it very easy for me to add new items to the user’s inventory. I am storing their inventory in my UserProfile model, and using a ManyToManyField for keeping track of the user’s items(with an intermediary ‘through’ model for keeping track of the quantity of the item), and that means that I can add items to the player’s inventory with a single line of code:

profile.inventoryitem_set.create(item=item,owner=profile)

With item being the item I want to add, and owner being the profile I am adding the item for.

One question that came up while building my inventory system was “Should items be stackable?” – because it makes sense for things like weapons not to stack, but things like usables to stack. In the end, I decided to add a stackable BooleanField to all of my items, and then just check it in my InventoryItem’s save() method, like so:

def save(self,*args,**kwargs):
	if self.item.stackable and kwargs.get('force_insert',False):
		self = InventoryItem.objects.get_or_create(item=self.item,owner=self.owner)[0]
		self.quantity += 1
		kwargs['force_insert'] = False
	super(InventoryItem, self).save(*args,**kwargs)

Is this the best way to do it? Probably not. But it lets me have items that do stack and items that don’t stack fairly easily, in addition to being able to add items to the player’s inventory without having to write a lot of boilerplate code.

Overall, progress is being made – while I’m not sure I will be able to finish as much as I would have liked to by the time that the contest is over (December 11th), I’m fairly confident that I will have a codebase completed that I am happy to work on far into the future.

Completed this week:

  • Basic combat system – needs some tweaking but currently workable
  • Inventory management – add items, remove items

Still to do:

  • Create more content and quests – while there are plans in place for upwards of 5 areas at the start of the game, there have only been quests for 2 of them designed so far.
  • Write better storyline content – right now it just says things like “the storyteller tells you to go over there. So you decide to do that.”
  • Lots of polishing and re-working – while most of the internals of the game work and are playable right now, they don’t feel “just right” yet.
]]> http://buildingbrowsergames.com/2008/11/03/rawrmys-inventory/feed/ 0 Rawrmy Starts http://buildingbrowsergames.com/2008/10/27/rawrmy-starts/ http://buildingbrowsergames.com/2008/10/27/rawrmy-starts/#comments Mon, 27 Oct 2008 14:00:32 +0000 Luke http://buildingbrowsergames.com/?p=527 This week was spent getting started on Rawrmy – building the initial systems, and planning out how the game will play out.

I have decided to build Rawrmy with Django – which is an MVC framework like Ruby on Rails(except in Python instead of Ruby).

Django has a vast number of freely available libraries for common functions, in addition to coming with some handy features bundled – like an auto-generating admin interface, and authentication systems that are pre-built for you(and will work for 90% of the things you’d need it for).

With that said, all of Rawrmy’s initial systems are built – login, registration, and profiles – mostly by taking advantage of the excellent django-registration library.

One of the stumbling blocks that I’ve encountered while working on Rawrmy is flexibility – while I’d like to make my systems as flexible as possible for the sake of future content, I am rapidly finding that there is a certain point where you need to trade flexibility for just writing the code. This is becoming most evident with the area exploration system – areas are currently a model in my database, and their code looks like this:

class Area(models.Model):
	title = models.CharField(max_length=500)
	slug = models.SlugField(blank=True)
	monsters = models.ManyToManyField('Monster',null=True,blank=True)
 
	def save(self,*args,**kwargs):
		if not self.slug:
			self.slug = slugify(self.title)
		super(Area,self).save(*args,**kwargs)
 
	def __unicode__(self):
		return self.title

Originally, my URLS looked like this:

url(r'explore/(?P<area_slug>.+)/$',views.explore,name='explore-area'),

I had planned to retrieve the area the user was exploring based on the slug, and then use that to figure out what happened when they explored that area. However, I quickly came up against issues with the flexibility of this approach – while it makes it easy to add more areas and allow users to explore them, it makes it very difficult for me as the developer to add custom behavior to an area. If I want to add custom logic to the Forest area but not the Mountain area, how am I supposed to do that using the current configuration?

With that in mind, my urlpatterns have changed, and I now hard-code the area slug, and map it to a specific view:

url(r'explore/forest/$',views.explore_forest,name='explore-forest'),

This way is a little less flexible in terms of being able to deploy new areas instantly, but it allows me to write any custom logic I need – which is what I was looking for.

Completed this week:

  • User management – login, logout, register
  • Escort management – choose escort
  • Class Choice – choose class

Still to do:

  • Exploring – needs a lot of fleshing out
  • Storyline – needs to be better (writer disappeared)
  • Hook – what makes this game fun?
]]> http://buildingbrowsergames.com/2008/10/27/rawrmy-starts/feed/ 0 Dropping Items (Perl) http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/ http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/#comments Thu, 23 Oct 2008 14:00:29 +0000 Luke http://buildingbrowsergames.com/?p=520 Now that we’ve built a way for users to buy items, we need a way for users to get items – by killing monsters. Today, we’ll be adding drops to our combat system.

To begin with, check out a recent copy of the source code for our tutorial:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 42

In order to keep track of the items that our monsters drop, we need to add another table to our database:

CREATE TABLE monster_items (
	id int NOT NULL AUTO_INCREMENT,
	monster_id int,
	item_id int,
	rarity int,
	PRIMARY KEY(id)
);

The monster_items table will be what we use to keep track of the items that monsters can drop after users kill them. Most of this table explains itself – but you might be wondering about what the ‘rarity’ column is there for. Essentially, the ‘rarity’ column is there for exactly what it says it’s there for; defining the rarity of a drop! We will use the value in the column to randomly determine which items drop from a monster – allowing us to have item A at 10% rarity, and item B at 90% rarity from the same monster.

With our table created, let’s move on to writing some code. We’ll get the ball rolling with a slight tweak to forest.tmpl:

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<p>You found a <strong><!--tmpl_var name='item'--></strong>!</p>

We will be using that extra piece of code in our template to display the item that the user gains after killing the monster.

With our template tweaked, we can move on to writing some actual code inside forest.cgi:

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my $rand = int(rand(100));
$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
$sth->execute($monsterID,$rand);
my $itemID;
$sth->bind_columns(\$itemID);
$sth->fetch;
$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
$sth->execute($userID,$itemID);
my $count;
$sth->bind_columns(\$count);
$sth->fetch;
if($count > 0) {
	# already has one of the item
	$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
} else {
	# has none of the item - new row
	$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
}
$sth->execute($userID,$itemID);
$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
$sth->execute($itemID);
$sth->bind_columns(\$parameters{item});
$sth->fetch;

If you’ve been paying attention, you might have noticed that this code is (for the most part), an exact copy of the code from our items shop from earlier. The only ‘new’ part of this code is the first 5 lines or so; it is there that we retrieve the new loot for the user. To begin with, we generate a random number between 0, and 100. While we don’t really need to pass the value through int(), it makes the number a lot simpler to work with(as it’s now 20, instead of 20.020859). Next, we use a single line of SQL to retrieve a random item for the player that is A) dropped by the monster, and B) has a rarity greater than or equal to the value that we randomly generated earlier. We use the ORDER BY RAND() clause to randomize within our results, and finally add LIMIT 1 to make sure that we only get one back. Once we’ve retrieved the random item to add to the player’s inventory, we’re finished – users can now received random items from the monsters that they kill in combat.

Here’s the updated forest.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
if(%arguments) {
	if($arguments{action} eq 'Attack') {
		# fighting the monster	
		use stats;
		use monsterstats;
		my $cookie = $query->cookie('username+password'); 
		my ($username) = split(/\+/,$cookie);
		$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
		$sth->execute($username);
		my $userID;
		$sth->bind_columns(\$userID);
		$sth->fetch;
		my %player = (
			name		=>	$username,
			attack		=>	stats::getStat('atk',$userID),
			defence		=>	stats::getStat('def',$userID),
			curhp		=>	stats::getStat('curhp',$userID)
		);
		my $phand = stats::getStat('phand',$userID);
		$player{attack} += weaponstats::getWeaponStat('atk',$phand);
		use armorstats;
		my @armor = qw(atorso ahead alegs aright aleft);
		foreach my $key(@armor) {
			my $id = stats::getStat($key,$userID);
			my $defence = armorstats::getArmorStat('defence',$id);
			$player{defence} += $defence;
		}		
		$sth = $dbh->prepare("SELECT id FROM monsters WHERE name = ?");
		$sth->execute($arguments{monster});
		my $monsterID;
		$sth->bind_columns(\$monsterID);
		$sth->fetch;
		my %monster = (
			name		=>	$arguments{monster},
			attack		=>	monsterstats::getMonsterStat('atk',$monsterID),
			defence		=>	monsterstats::getMonsterStat('def',$monsterID),
			curhp		=>	monsterstats::getMonsterStat('maxhp',$monsterID)
		);
		my @combat;
		my $turns = 0;
		my ($attacker,$defender);
		while($player{curhp} > 0 && $monster{curhp} > 0) {
			my %attack;
			if($turns % 2 != 0) {
				$attacker = \%monster;
				$defender = \%player;
			} else {
				$attacker = \%player;
				$defender = \%monster;
			}
			my $damage = 0;
			if($attacker->{attack} > $defender->{defence}) {
				$damage = $attacker->{attack} - $defender->{defence};	
			}
			my %attack = (
				attacker => $attacker->{name},
				defender => $defender->{name},
				damage => $damage
			);
			$defender->{curhp} -= $damage;
			push @combat, \%attack;
			$turns++;
		}
		stats::setStat('curhp',$userID,$player{curhp});
		if($player{curhp} > 0) {
			# player won
			stats::setStat('gc',$userID,stats::getStat('gc',$userID) + monsterstats::getMonsterStat('gc',$monsterID));
			$parameters{won} = 1;
			$parameters{gold} = monsterstats::getMonsterStat('gc',$monsterID);
			my $rand = int(rand(99))+1;
			$sth = $dbh->prepare("SELECT item_id FROM monster_items WHERE monster_id = ? AND rarity >= ? ORDER BY RAND() LIMIT 1");
			$sth->execute($monsterID,$rand);
			my $itemID;
			$sth->bind_columns(\$itemID);
			$sth->fetch;
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$sth = $dbh->prepare("SELECT name FROM items WHERE id = ?");
			$sth->execute($itemID);
			$sth->bind_columns(\$parameters{item});
			$sth->fetch;
		} else {
			# monster won	
			$parameters{lost} = 1;
		}
		$parameters{combat} = \@combat;
	} else {
		# running away - back to the index page!
		print $query->redirect('index.cgi');
	}	
} else {
	$sth = $dbh->prepare("SELECT name FROM monsters ORDER BY RAND() LIMIT 1");
	$sth->execute();
	my $monster;
	$sth->bind_columns(\$monster);
	$sth->fetch;
	$parameters{monster} = $monster;
}
 
 
my $template = HTML::Template->new(
		filename	=>	'forest.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

Extra Credit

  • Change the ‘you found an item’ message to also display the total quantity of the item that is in the user’s inventory.
]]> http://buildingbrowsergames.com/2008/10/23/dropping-items-perl/feed/ 0 Using Items (Perl) http://buildingbrowsergames.com/2008/10/17/using-items-perl/ http://buildingbrowsergames.com/2008/10/17/using-items-perl/#comments Fri, 17 Oct 2008 14:00:31 +0000 Luke http://buildingbrowsergames.com/?p=491 Our game is still missing something really important: items that users can actually use!

Today, we’ll be writing the code that allows our users to use the items in their inventory. To start off, check out a copy of the code for our project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 38

And then we’re ready to go!

To start off, we’ll build a basic template for our inventory page, and put it inside inventory.tmpl:

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<tmpl_if name='message'>
		<p><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<strong><!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'--></strong>
			<form action='inventory.cgi' method='post'>
				<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
				<input type='submit' value='Use' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
</body>
</html>

With our template built, we can start writing the code inside inventory.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
 
my $template = HTML::Template->new(
		filename	=>	'inventory.tmpl',
		associate	=>	$query,
		die_on_bad_params => 0,
	);
$template->param(%parameters);
print $query->header(), $template->output;

This code is almost entirely from our item shop code – so there isn’t really anything you haven’t seen before. The one new piece is the die_on_bad_params parameter that we are passing to HTML::Template->new() – we do this so that it won’t complain about the fact that our @inventory variable has the value ‘item_id’ inside of it, but the template doesn’t.

Our code is still missing something, however: the ability to actually use items!

If you remember the initial database preparations that we did earlier, you’ll remember that we created a new stat called ‘Item Use Token’ – and now we’ll be putting that stat to use. We will be using the ‘Item Use Token’ stat in conjunction with what’s known as a Dispatch Table to easily write the code that will run when our items are used.

For now, we’ll insert a single item with the token ‘potion’:

INSERT INTO items(name,type,price) VALUES ('Red Potion','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Red Potion'),'potion','Item');

With that stat set up, we can buckle down and start on our dispatch table.

Dispatch tables are one of the more useful tools available to you as a programmer; they allow you to create a hash of functions(instead of values), and then call functions by key. This makes them perfect for our items system, because using dispatch tables will allow us to easily add new code for items in the most efficient manner possible. Let’s write some code to define and interact with a dispatch table:

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my %actions = (
	'potion' => \&use_potion,
);
 
sub use_potion {
	$parameters{message} = 'This is code that would run if the user used a potion.';
}
 
if(%arguments) {
	if($arguments{'item-id'}) {
		use items;
		$sth = $dbh->prepare("SELECT item_id FROM user_items WHERE user_id = ? AND id = ?");
		$sth->execute($userID,$arguments{'item-id'});
		my $itemID;
		$sth->bind_columns(\$itemID);
		$sth->fetch;
		my $token = items::getStat('token',$itemID);
		$actions{$token}->();
	}
}

If you visit your inventory page and click on ‘Use’ underneath the item in your character’s inventory, you should be treated to the simple message ‘This is code that would run when the user used a potion’. Neat, eh?

While we’ve built the functionality for a single item, that’s not really our use-case – we need to see how useful this system will be if we want to add another item without writing too much extra code. Ideally, we would only need to write the code that makes this item special – and thankfully, dispatch tables let us do just that. First, we’ll add another item, with the token ‘crystal_ball’:

INSERT INTO items(name,type,price) VALUES ('Crystal Ball','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Crystal Ball'),'crystal_ball','Item');

And now that we’ve added the item, we’ll add the code to run when an item with that token gets used:

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my %actions = (
	'potion' => \&use_potion,
	'crystal_ball'	=>	\&use_crystal_ball,
);
 
sub use_crystal_ball {
	$parameters{message} = 'This is code that would run if the user used a crystal ball.';
}

And if you use the crystal ball now that we’ve written that code, you’ll see the message ‘This is code that would run if the user used a crystal ball.’.

The ability to keep our code organized in this way is what makes dispatch tables so useful – it doesn’t take us long at all to write more code to support any new items we want to add, and it’s as simple as just adding a new token(which serves as a key in the dispatch table), and then writing the function that will be called(you could even map multiple tokens to the same function, if you wanted to – although in that situation you should just have two items with the same token).

And with that, our inventory page is complete! Users can now use any items that you have defined tokens and written the code for – and you can run any code that should be executed no matter what the item’s token is by adding it just after the line that says:

$actions{$token}->();

Here’s the (slightly re-organized) code for inventory.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
my %actions = (
	'potion' => \&use_potion,
	'crystal_ball'	=>	\&use_crystal_ball,
);
 
sub use_crystal_ball {
	$parameters{message} = 'This is code that would run if the user used a crystal ball.';
}
 
sub use_potion {
	$parameters{message} = 'This is code that would run if the user used a potion.';
}
 
if(%arguments) {
	if($arguments{'item-id'}) {
		use items;
		$sth = $dbh->prepare("SELECT item_id FROM user_items WHERE user_id = ? AND id = ?");
		$sth->execute($userID,$arguments{'item-id'});
		my $itemID;
		$sth->bind_columns(\$itemID);
		$sth->fetch;
		my $token = items::getStat('token',$itemID);
		$actions{$token}->();
	}
}
 
$sth = $dbh->prepare("SELECT id, item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
 
my $template = HTML::Template->new(
		filename	=>	'inventory.tmpl',
		associate	=>	$query,
		die_on_bad_params => 0,
	);
$template->param(%parameters);
print $query->header(), $template->output;

And here’s inventory.tmpl:

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<tmpl_if name='message'>
		<p><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<strong><!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'--></strong>
			<form action='inventory.cgi' method='post'>
				<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
				<input type='submit' value='Use' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
</body>
</html>

Extra Credit

  • Re-factor the weapons and armor systems, so that they are all sold from the item-shop – and when you use them from your inventory, the items are equipped.
]]> http://buildingbrowsergames.com/2008/10/17/using-items-perl/feed/ 0 Using Items (PHP) http://buildingbrowsergames.com/2008/10/16/using-items-php/ http://buildingbrowsergames.com/2008/10/16/using-items-php/#comments Thu, 16 Oct 2008 14:00:17 +0000 Luke http://buildingbrowsergames.com/?p=488 What game is complete without usable items? Not ours, that’s for sure!

With that in mind, today we are going to write the code that makes items usable. To start off, check out a copy of the code for our project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/php/pbbg tutorial -r 37

And then we’re ready to go!

To start off, we’ll build a basic template for our inventory page, and put it inside inventory.tpl:

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<ul>
		{foreach from=$inventory key=id item=i}
		<li>
			<strong>{$i.name} x {$i.quantity}</strong>
			<form action='inventory.php' method='post'>
				<input type='hidden' name='item-id' value='{$i.id}' />
				<input type='submit' value='Use' />
			</form>
		</li>
		{/foreach}
	</ul>
</body>
</html>

With the template built, we can get started on the code for inventory.php:

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<?php
 
require_once 'smarty.php';
 
session_start();
 
require_once 'config.php';		// our database settings
$conn = mysql_connect($dbhost,$dbuser,$dbpass)
	or die('Error connecting to mysql');
mysql_select_db($dbname);
// retrieve player's ID
$query = sprintf("SELECT id FROM users WHERE UPPER(username) = UPPER('%s')",
			mysql_real_escape_string($_SESSION['username']));
$result = mysql_query($query);
list($userID) = mysql_fetch_row($result);
 
$inventory = array();
$query = sprintf("SELECT id, item_id, quantity FROM user_items WHERE user_id = '%s'",
		mysql_real_escape_string($userID));
$result = mysql_query($query);
while($row = mysql_fetch_assoc($result)) {
	 $item_query = sprintf("SELECT name FROM items WHERE id = '%s'",
		mysql_real_escape_string($row['item_id']));
	$item_result = mysql_query($item_query);
	list($row['name']) = mysql_fetch_row($item_result);
	array_push($inventory,$row);
}
$smarty->assign('inventory',$inventory);
$smarty->display('inventory.tpl');
 
?>

This code is essentially taken straight from our item shop code – but it’s missing one key thing: the ability to actually use items!

If you remember our initial database preparations, you’ll remember that we inserted a new stat called ‘Item Use Token’ – and this is where that stat will come into play. We will be using the ‘Item Use Token’ stat and something known as a Dispatch Table to easily write arbitrary code that can be run whenever our items are used.

For now, we’ll insert a single item with the use token of ‘potion’:

INSERT INTO items(name,type,price) VALUES ('Red Potion','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Red Potion'),'potion','Item');

With that token in place, we will be able to start writing our dispatch table.

Dispatch Tables are a bit of a strange beast; essentially, what you end up doing when you create a dispatch table is creating an associative array, filled with function definitions(instead of values). Then, you use a certain key value to retrieve the function you are supposed to call. This is actually perfect for items system, because it will allow us to easily add new and different types of items anytime we want or need to(by simply adding another token, and then writing the code to handle it). Let’s get started on our dispatch table:

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function use_potion() {
	echo 'This is code that would run when the user used a potion.';
}
$actions = array('potion' => 'use_potion');
 
if($_POST) {
	if($_POST['item-id']) {
		$query = sprintf("SELECT item_id FROM user_items WHERE user_id = '%s' AND id = '%s'",
			mysql_real_escape_string($userID),
			mysql_real_escape_string($_POST['item-id']));
		$result = mysql_query($query);
		list($itemID) = mysql_fetch_row($result);
		require_once 'items.php';
		$token = getItemStat('token',$itemID);
		call_user_func($actions[$token]);
	}
}

And if you visit your inventory page and click ‘Use’ on the item in your character’s inventory, you should be treated to the simple message ‘This is code that would run when the user used a potion.’. Neat, eh?

While this shows you how to build this functionality for a single item, single items aren’t really what this code is geared towards. So let’s add another item and type:

INSERT INTO items(name,type,price) VALUES ('Crystal Ball','Usable',10);
	INSERT INTO entity_stats(stat_id,entity_id,value,entity_type) VALUES ((SELECT id FROM stats WHERE short_name='token'),(SELECT id FROM items WHERE name='Crystal Ball'),'crystal_ball','Item');

Now that we’ve added another item token to handle, we’ll write the code that gets run when an item with that token gets used:

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	function use_crystal_ball() {
		echo 'This is code that would run when the user used a crystal ball.';
	}
	$actions = array('potion' => 'use_potion','crystal_ball' => 'use_crystal_ball');

And now if you use a crystal ball, you will get the message ‘This is code that would run when the user used a crystal ball.’.

This is why dispatch tables are so useful – it doesn’t take us long at all to write more code to support more items anytime we need to.

With that, our inventory page is essentially finished! You can run any code that should run after any item is used by running it just after the call to call_user_func(), and you can run any code specific to that item token by defining it within the $actions array. Handy!

Here’s the (slightly re-organized) code for inventory.php:

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<?php
 
require_once 'smarty.php';
 
session_start();
 
require_once 'config.php';		// our database settings
$conn = mysql_connect($dbhost,$dbuser,$dbpass)
	or die('Error connecting to mysql');
mysql_select_db($dbname);
// retrieve player's ID
$query = sprintf("SELECT id FROM users WHERE UPPER(username) = UPPER('%s')",
			mysql_real_escape_string($_SESSION['username']));
$result = mysql_query($query);
list($userID) = mysql_fetch_row($result);
 
$actions = array('potion' => 'use_potion','crystal_ball' => 'use_crystal_ball');
 
if($_POST) {
	if($_POST['item-id']) {
		$query = sprintf("SELECT item_id FROM user_items WHERE user_id = '%s' AND id = '%s'",
			mysql_real_escape_string($userID),
			mysql_real_escape_string($_POST['item-id']));
		$result = mysql_query($query);
		list($itemID) = mysql_fetch_row($result);
		require_once 'items.php';
		$token = getItemStat('token',$itemID);
		call_user_func($actions[$token]);
	}
}
 
$inventory = array();
$query = sprintf("SELECT id, item_id, quantity FROM user_items WHERE user_id = '%s'",
		mysql_real_escape_string($userID));
$result = mysql_query($query);
while($row = mysql_fetch_assoc($result)) {
	 $item_query = sprintf("SELECT name FROM items WHERE id = '%s'",
		mysql_real_escape_string($row['item_id']));
	$item_result = mysql_query($item_query);
	list($row['name']) = mysql_fetch_row($item_result);
	array_push($inventory,$row);
}
$smarty->assign('inventory',$inventory);
$smarty->display('inventory.tpl');
 
function use_potion() {
	echo 'This is code that would run when the user used a potion.';
}
function use_crystal_ball() {
	echo 'This is code that would run when the user used a crystal ball.';
}
?>

And here’s the template(inventory.tpl):

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<html>
<head>
	<title>Your Inventory</title>
</head>
<body>
	<p>This is your inventory. Check out all the stuff you've got!</p>
	<ul>
		{foreach from=$inventory key=id item=i}
		<li>
			<strong>{$i.name} x {$i.quantity}</strong>
			<form action='inventory.php' method='post'>
				<input type='hidden' name='item-id' value='{$i.id}' />
				<input type='submit' value='Use' />
			</form>
		</li>
		{/foreach}
	</ul>
</body>
</html>

Extra Credit

  • Build healing potions that heal the player for 10, 20, or 30 HP (you may need to add another stat to the item to do this).
]]> http://buildingbrowsergames.com/2008/10/16/using-items-php/feed/ 8 Buying Items (Perl) http://buildingbrowsergames.com/2008/10/14/buying-items-perl/ http://buildingbrowsergames.com/2008/10/14/buying-items-perl/#comments Tue, 14 Oct 2008 14:00:31 +0000 Luke http://buildingbrowsergames.com/?p=484 We’ve already run the initial database code to get our items system prepared, and now it’s time to write the code that is responsible for interacting with it. Today, we’ll build the items shop.

In order to get started, check out a copy of our code from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/perl/pbbg tutorial -r 36

With that done, we’re ready to get started building our item system!

For starters, we’ll build an item shop – because we need players to be able to get items into their inventory before they can interact with them. We’ll start off with just about the same template code as we had for our armor and weapons shops, inside of item-shop.tmpl:

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<html>
<head>
	<title>The Item Shop</title>
</head>
<body>
	<p>Welcome to the Item Shop.</p>
	<p><a href='index.cgi'>Back to main</a></p>
	<h3>Current Inventory:</h3>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'-->
			<form action='item-shop.cgi' method='post'>
				<input type='hidden' name='sell' value='<!--tmpl_var name="item_id"-->' />
				<input type='submit' value='Sell' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
	<p>You may purchase any of the items listed below.</p>
	<tmpl_if name='error'>
		<p style='color:red'><!--tmpl_var name='error'--></p>
	</tmpl_if>
	<tmpl_if name='message'>
		<p style='color:green'><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='items'>
			<li>
				<strong><!--tmpl_var name='name'--></strong> - <em><!--tmpl_var name='price'--> gold coins</em>
				<form action='item-shop.cgi' method='post'>
					<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
					<input type='submit' value='Buy' />
				</form>
			</li>
		</tmpl_loop>
	</ul>
</body>
</html>

This is essentially the same template as our other shops – the only difference is the ‘Current Inventory’ display. The current inventory is pretty self-explanatory; it will display the user’s current inventory whenever they visit the shop. Let’s start writing the code for our shop, inside item-shop.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
$sth = $dbh->prepare("SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' LIMIT 5");
$sth->execute();
my @items = ();
while(my $row = $sth->fetchrow_hashref) {
	push @items, $row;
}
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
$parameters{items} = \@items;
 
my $template = HTML::Template->new(
		filename	=>	'item-shop.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

For the most part, this is all code we’ve written before. The only ‘new’ code here is the inventory retrieval code, on lines 36-43. We retrieve all of the rows in user_items that are linked to the current user, and then store them into our @inventory array so that we can display them. We also retrieve and store the name of the item, so that it will display with something a little easier for the player to understand than ‘18′(which is currently a ‘Red Potion’ in the sample game).

Now that we can display items, we should write some code so users can buy them:

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if(%arguments) {
	if($arguments{'item-id'}) {
		my $itemID = $arguments{'item-id'};
		$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
		$sth->execute($itemID);
		my $price;
		$sth->bind_columns(\$price);
		$sth->fetch;
		my $gold = stats::getStat('gc',$userID);
		if($gold >= $price) {
			stats::setStat('gc',$userID,($gold - $price));
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$parameters{message} = 'You purchased the item.';
		} else {
			$parameters{error} = 'You cannot afford that item!';
		}		
	}
}

If you’re comparing this to the code from our weapons or armor shops from earlier, you might notice some differences – like the fact that we’re running two queries to add items to the player’s inventory, instead of just one. This is because our user inventory has been built in such a way that items can ’stack’ – meaning you can have more than one of any particular item. Because we only need to keep track of the fact that a player has <x> of an item, we just use a column inside user_items to keep track of the quantity of the item that the player currently has in their inventory. Because we’re storing our data in this way, whenever we want to add an item to a player’s inventory, we need to first check and see if a row exists – if it does, we increment the quantity of the item. If it doesn’t, we’ll insert a new row.

Now that that’s finished, there’s only one more thing our item shop is missing – the ability to sell items! We’ll quickly add our item selling code to item-shop.cgi:

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} elsif($arguments{sell}) {
	my $itemID = $arguments{sell};
	$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
	$sth->execute($itemID);
	my $price;
	$sth->bind_columns(\$price);
	$sth->fetch;
	my $gold = stats::getStat('gc',$userID);
	stats::setStat('gc',$userID,($gold + $price));
	$sth = $dbh->prepare("SELECT quantity FROM user_items WHERE user_id = ? AND item_id = ?");
	$sth->execute($userID,$itemID);
	my $quantity;
	$sth->bind_columns(\$quantity);
	$sth->fetch;
	if($quantity > 1) {
		$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = ? AND item_id = ?");
	} else {
		$sth = $dbh->prepare("DELETE FROM user_items WHERE user_id = ? AND item_id = ?");
	}
	$sth->execute($userID,$itemID);
	$parameters{message} = 'You sold the item.';
}

This code is pretty similar to the code from our other shops, except for the different method used to update the information in the database. In the ‘buy item’ code(2 blocks above), we used ‘SELECT COUNT’ to check to see if a row existed – in this case, because we need to see how many of the item the player has, we just use a ‘SELECT’ statement to retrieve the quantity of the item that the player has. Based on the value we retrieve, we perform one of two queries – an UPDATE query if they have more than 1, and a DELETE query if they have only 1 of the item. Performing the DELETE query removes the row from the user_items table, which helps us make sure that we are only storing data we need.

With that code written, we’re done! We have a working item shop now, and our inventory system is beginning to take shape. Don’t forget to link to it from your main page:

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<p><a href='item-shop.cgi'>The Item Shop</a></p>

And that’s that! Here’s the code from item-shop.tmpl:

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<html>
<head>
	<title>The Item Shop</title>
</head>
<body>
	<p>Welcome to the Item Shop.</p>
	<p><a href='index.cgi'>Back to main</a></p>
	<h3>Current Inventory:</h3>
	<ul>
		<tmpl_loop name='inventory'>
		<li>
			<!--tmpl_var name='name'--> x <!--tmpl_var name='quantity'-->
			<form action='item-shop.cgi' method='post'>
				<input type='hidden' name='sell' value='<!--tmpl_var name="item_id"-->' />
				<input type='submit' value='Sell' />
			</form>
		</li>
		</tmpl_loop>
	</ul>
	<p>You may purchase any of the items listed below.</p>
	<tmpl_if name='error'>
		<p style='color:red'><!--tmpl_var name='error'--></p>
	</tmpl_if>
	<tmpl_if name='message'>
		<p style='color:green'><!--tmpl_var name='message'--></p>
	</tmpl_if>
	<ul>
		<tmpl_loop name='items'>
			<li>
				<strong><!--tmpl_var name='name'--></strong> - <em><!--tmpl_var name='price'--> gold coins</em>
				<form action='item-shop.cgi' method='post'>
					<input type='hidden' name='item-id' value='<!--tmpl_var name="id"-->' />
					<input type='submit' value='Buy' />
				</form>
			</li>
		</tmpl_loop>
	</ul>
</body>
</html>

And here’s the (slightly tweaked) code from item-shop.cgi:

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#!/usr/bin/perl -w
 
use strict;
use CGI qw(:cgi);
use CGI::Carp qw(fatalsToBrowser warningsToBrowser);
use HTML::Template;
use DBI;
use config;
 
my $query = new CGI;
my %arguments = $query->Vars;
 
my $dbh = DBI->connect("DBI:mysql:$config{dbName}:$config{dbHost}",$config{dbUser},$config{dbPass},{RaiseError => 1});
my $sth;
my %parameters;
 
use stats;
 
my $cookie = $query->cookie('username+password');
my ($username) = split(/\+/,$cookie);
$sth = $dbh->prepare("SELECT id FROM users WHERE UPPER(username) = UPPER(?)");
$sth->execute($username);
my $userID;
$sth->bind_columns(\$userID);
$sth->fetch;
 
if(%arguments) {
	my $price;
	my $itemID;
	$itemID = $arguments{'item-id'} ? $arguments{'item-id'} : $arguments{sell};
	$sth = $dbh->prepare("SELECT price FROM items WHERE id = ?");
	$sth->execute($itemID);
	$sth->bind_columns(\$price);
	$sth->fetch;
	my $gold = stats::getStat('gc',$userID);
	if($arguments{'item-id'}) {
		if($gold >= $price) {
			stats::setStat('gc',$userID,($gold - $price));
			$sth = $dbh->prepare("SELECT count(id) FROM user_items WHERE user_id = ? AND item_id = ?");
			$sth->execute($userID,$itemID);
			my $count;
			$sth->bind_columns(\$count);
			$sth->fetch;
			if($count > 0) {
				# already has one of the item
				$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = ? AND item_id = ?");
			} else {
				# has none of the item - new row
				$sth = $dbh->prepare("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,?,?)");
			}
			$sth->execute($userID,$itemID);
			$parameters{message} = 'You purchased the item.';
		} else {
			$parameters{error} = 'You cannot afford that item!';
		}		
	} elsif($arguments{sell}) {
		stats::setStat('gc',$userID,($gold + $price));
		$sth = $dbh->prepare("SELECT quantity FROM user_items WHERE user_id = ? AND item_id = ?");
		$sth->execute($userID,$itemID);
		my $quantity;
		$sth->bind_columns(\$quantity);
		$sth->fetch;
		if($quantity > 1) {
			$sth = $dbh->prepare("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = ? AND item_id = ?");
		} else {
			$sth = $dbh->prepare("DELETE FROM user_items WHERE user_id = ? AND item_id = ?");
		}
		$sth->execute($userID,$itemID);
		$parameters{message} = 'You sold the item.';
	}
}
 
$sth = $dbh->prepare("SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' LIMIT 5");
$sth->execute();
my @items = ();
while(my $row = $sth->fetchrow_hashref) {
	push @items, $row;
}
 
$sth = $dbh->prepare("SELECT item_id, quantity FROM user_items WHERE user_id = ?");
$sth->execute($userID);
my @inventory = ();
while(my $row = $sth->fetchrow_hashref) {
	my $sth2 = $dbh->prepare("SELECT name FROM items WHERE id = ?");
	$sth2->execute($row->{item_id});
	$sth2->bind_columns(\$row->{name});
	$sth2->fetch;
	push @inventory, $row;
}
 
$parameters{inventory} = \@inventory;
$parameters{items} = \@items;
 
my $template = HTML::Template->new(
		filename	=>	'item-shop.tmpl',
		associate	=>	$query,
	);
$template->param(%parameters);
print $query->header(), $template->output;

Extra Credit

  • Can you modify the item shop so that it sells all types of items?
]]> http://buildingbrowsergames.com/2008/10/14/buying-items-perl/feed/ 0 Buying Items (PHP) http://buildingbrowsergames.com/2008/10/13/buying-items/ http://buildingbrowsergames.com/2008/10/13/buying-items/#comments Mon, 13 Oct 2008 14:00:17 +0000 Luke http://buildingbrowsergames.com/?p=480 Today, we’re going to build the items shop for our game. We’ve already run the initial database code to get everything prepared, and now it’s just a matter of writing the code to interact with it.

To begin with, check out a copy of our code from the Google Code Project:

svn checkout http://building-browsergames-tutorial.googlecode.com/svn/trunk/php/pbbg tutorial -r 36

And now we’re ready to get started on building our items system!

The first thing that we will need to build is our items shop. We’ll start off with the same template as our armor and weapons shops, but put this one inside item-shop.tpl:

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	<html>
	<head>
		<title>The Item Shop</title>
	</head>
	<body>
		<p>Welcome to the Item Shop.</p>
		<p><a href='index.php'>Back to main</a></p>
		<h3>Current Inventory:</h3>
		<ul>
			{foreach from=$inventory key=item_id item=i}
			<li>
				{$i.name} x {$i.quantity}
				<form action='item-shop.php' method='post'>
					<input type='hidden' name='sell-id' value='{$i.item_id}' />
					<input type='submit' value='Sell' />
				</form>
			</li>
			{/foreach}
		</ul>
		<p>You may purchase any of the items listed below.</p>
		{if $error ne ''}
			<p style='color:red'>{$error}</p>
		{/if}
		{if $message ne ''}
			<p style='color:green'>{$message}</p>
		{/if}
		<ul>
			{foreach from=$items key=id item=i}
				<li>
					<strong>{$i.name}</strong> - <em>{$i.price} gold coins</em>
					<form action='item-shop.php' method='post'>
						<input type='hidden' name='item-id' value='{$i.id}' />
						<input type='submit' value='Buy' />
					</form>
			{/foreach}
		</ul>
	</body>
	</html>

As you can see, this is largely the same template as with our other shops – with the one difference being the ‘Current Inventory’ display(as opposed to current weapons/armor in the other shops). When the user visits this shop, we will retrieve and display the contents of their inventory as well. With that being said, let’s start writing the code for the item shop inside item-shop.php:

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<?php
 
require_once 'smarty.php';
 
session_start();
 
require_once 'config.php';		// our database settings
$conn = mysql_connect($dbhost,$dbuser,$dbpass)
	or die('Error connecting to mysql');
mysql_select_db($dbname);
// retrieve player's ID
$query = sprintf("SELECT id FROM users WHERE UPPER(username) = UPPER('%s')",
			mysql_real_escape_string($_SESSION['username']));
$result = mysql_query($query);
list($userID) = mysql_fetch_row($result);
require_once 'stats.php';	// player stats
$query = "SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' ORDER BY RAND() LIMIT 5;";
$result = mysql_query($query);
$items = array();
while($row = mysql_fetch_assoc($result)) {
	array_push($items,$row);
}
$inventory = array();
$query = sprintf("SELECT id, item_id, quantity FROM user_items WHERE user_id = '%s'",
		mysql_real_escape_string($userID));
$result = mysql_query($query);
while($row = mysql_fetch_assoc($result)) {
	 $item_query = sprintf("SELECT name FROM items WHERE id = '%s'",
		mysql_real_escape_string($row['item_id']));
	$item_result = mysql_query($item_query);
	list($row['name']) = mysql_fetch_row($item_result);
	array_push($inventory,$row);
}
$smarty->assign('inventory',$inventory);
$smarty->assign('items',$items);
$smarty->display('item-shop.tpl');
 
?>

For the most part, this is all review – the only interesting and new code that we’ve written is the code appearing between lines 23 and 33 – our inventory retrieval code. We retrieve all rows from our user_items table that are linked to the User ID of the player who is currently logged in, and then just loop through them and put them into our $inventory array – but not before also retrieving the name of the item(so that we can display it a little nicer).

Now that we’ve got displaying items down, we’ll want to write some code so that users can actually buy them:

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if($_POST) {
	if($_POST['item-id']) {
		$itemID = $_POST['item-id'];
		$query = sprintf("SELECT price FROM items WHERE id = '%s'",mysql_real_escape_string($itemID));
		$result = mysql_query($query);
		list($cost) = mysql_fetch_row($result);
		$gold = getStat('gc',$userID);
		if($gold >= $cost) {
			setStat('gc',$userID,($gold - $cost));
			$query = sprintf("SELECT count(id) FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
				mysql_real_escape_string($userID),mysql_real_escape_string($itemID));
			$result = mysql_query($query);
			list($count) = mysql_fetch_row($result);
			if ($count > 0) {
				# already has one of the item
				$query = sprintf("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = '%s' AND item_id = '%s'",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			} else {
				# has none - new row
				$query = sprintf("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,'%s','%s')",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			}
			mysql_query($query);
			$smarty->assign('message','You purchased the item.');
		} else {
			$smarty->assign('error','You cannot afford that item!');
		}
	}
}

While that’s definitely a lot more code than we wrote to purchase weapons or armor, it’s still pretty simple once you take a look at it – essentially, once we get past the generic ‘do you have enough gold for this?’ check, we add the item to the user’s inventory. Because usable items can stack, we need to check if there is already a row in place for them or not. If there is no row in place, we insert a new one with the proper values(user ID, itemID, and quantity of 1). Otherwise, we just run an UPDATE statement on our table, to increment the quantity of the item for the player by 1.

Now that that’s finished, we only have one more thing to add to our item shop – the ability to sell items! We’ll quickly add that code to item-shop.php:

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} else if($_POST['sell-id']) {
	$itemID = $_POST['sell-id'];
	$query = sprintf("SELECT price FROM items WHERE id = '%s'",mysql_real_escape_string($itemID));
	$result = mysql_query($query);
	list($cost) = mysql_fetch_row($result);
	$gold = getStat('gc',$userID);
	setStat('gc',$userID,($gold + $cost));		
	$query = sprintf("SELECT quantity FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
		mysql_real_escape_string($userID),mysql_real_escape_string($itemID));
	$result = mysql_query($query);
	list($quantity) = mysql_fetch_row($result);
	if ($quantity > 1) {
		$query = sprintf("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = '%s' AND item_id = '%s'",
			mysql_real_escape_string($userID),
			mysql_real_escape_string($itemID));
	} else {
		$query = sprintf("DELETE FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
			mysql_real_escape_string($userID),
			mysql_real_escape_string($itemID));
	}
	mysql_query($query);		
	$smarty->assign('message','You sold the item.');
}

This code is almost the exact same as the ‘buy item’ code, except for some small differences:

  • First, we are selecting quantity instead of COUNT(id) from user_items. Selecting the COUNT will tell us if a row exists or not – but it won’t tell us how many of the item the player has. user_items.quantity will.
  • Based on how many of the item the user has left, we perform one of two different queries: either an UPDATE query to decrement the quantiy of the item by 1, or a DELETE query – to remove the row from the user_items table if it will no longer be needed.

With all that code written, we’re finished! We now have a working item shop, and the beginnings of our inventory system up and running. Don’t forget to add a link to the item shop from the main page:

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<p><a href='item-shop.php'>The Item Shop</a></p>

And that’s it! Here’s the code for item-shop.tpl:

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<html>
<head>
	<title>The Item Shop</title>
</head>
<body>
	<p>Welcome to the Item Shop.</p>
	<p><a href='index.php'>Back to main</a></p>
	<h3>Current Inventory:</h3>
	<ul>
		{foreach from=$inventory key=item_id item=i}
		<li>
			{$i.name} x {$i.quantity}
			<form action='item-shop.php' method='post'>
				<input type='hidden' name='sell-id' value='{$i.item_id}' />
				<input type='submit' value='Sell' />
			</form>
		</li>
		{/foreach}
	</ul>
	<p>You may purchase any of the items listed below.</p>
	{if $error ne ''}
		<p style='color:red'>{$error}</p>
	{/if}
	{if $message ne ''}
		<p style='color:green'>{$message}</p>
	{/if}
	<ul>
		{foreach from=$items key=id item=i}
			<li>
				<strong>{$i.name}</strong> - <em>{$i.price} gold coins</em>
				<form action='item-shop.php' method='post'>
					<input type='hidden' name='item-id' value='{$i.id}' />
					<input type='submit' value='Buy' />
				</form>
		{/foreach}
	</ul>
</body>
</html>

And item-shop.php:

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<?php
 
require_once 'smarty.php';
 
session_start();
 
require_once 'config.php';		// our database settings
$conn = mysql_connect($dbhost,$dbuser,$dbpass)
	or die('Error connecting to mysql');
mysql_select_db($dbname);
// retrieve player's ID
$query = sprintf("SELECT id FROM users WHERE UPPER(username) = UPPER('%s')",
			mysql_real_escape_string($_SESSION['username']));
$result = mysql_query($query);
list($userID) = mysql_fetch_row($result);
require_once 'stats.php';	// player stats
if($_POST) {
	if($_POST['item-id']) {
		$itemID = $_POST['item-id'];
		$query = sprintf("SELECT price FROM items WHERE id = '%s'",mysql_real_escape_string($itemID));
		$result = mysql_query($query);
		list($cost) = mysql_fetch_row($result);
		$gold = getStat('gc',$userID);
		if($gold >= $cost) {
			setStat('gc',$userID,($gold - $cost));
			$query = sprintf("SELECT count(id) FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
				mysql_real_escape_string($userID),mysql_real_escape_string($itemID));
			$result = mysql_query($query);
			list($count) = mysql_fetch_row($result);
			if ($count > 0) {
				# already has one of the item
				$query = sprintf("UPDATE user_items SET quantity = quantity + 1 WHERE user_id = '%s' AND item_id = '%s'",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			} else {
				# has none - new row
				$query = sprintf("INSERT INTO user_items(quantity,user_id,item_id) VALUES (1,'%s','%s')",
					mysql_real_escape_string($userID),
					mysql_real_escape_string($itemID));
			}
			mysql_query($query);
			$smarty->assign('message','You purchased the item.');
		} else {
			$smarty->assign('error','You cannot afford that weapon!');
		}
	} else if($_POST['sell-id']) {
		$itemID = $_POST['sell-id'];
		$query = sprintf("SELECT price FROM items WHERE id = '%s'",mysql_real_escape_string($itemID));
		$result = mysql_query($query);
		list($cost) = mysql_fetch_row($result);
		$gold = getStat('gc',$userID);
		setStat('gc',$userID,($gold + $cost));		
		$query = sprintf("SELECT quantity FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
			mysql_real_escape_string($userID),mysql_real_escape_string($itemID));
		$result = mysql_query($query);
		list($quantity) = mysql_fetch_row($result);
		if ($quantity > 1) {
			$query = sprintf("UPDATE user_items SET quantity = quantity - 1 WHERE user_id = '%s' AND item_id = '%s'",
				mysql_real_escape_string($userID),
				mysql_real_escape_string($itemID));
		} else {
			$query = sprintf("DELETE FROM user_items WHERE user_id = '%s' AND item_id = '%s'",
				mysql_real_escape_string($userID),
				mysql_real_escape_string($itemID));
		}
		mysql_query($query);		
		$smarty->assign('message','You sold the item.');
	}
}
$query = "SELECT DISTINCT(id), name, price FROM items WHERE type = 'Usable' ORDER BY RAND() LIMIT 5;";
$result = mysql_query($query);
$items = array();
while($row = mysql_fetch_assoc($result)) {
	array_push($items,$row);
}
$inventory = array();
$query = sprintf("SELECT id, item_id, quantity FROM user_items WHERE user_id = '%s'",
		mysql_real_escape_string($userID));
$result = mysql_query($query);
while($row = mysql_fetch_assoc($result)) {
	 $item_query = sprintf("SELECT name FROM items WHERE id = '%s'",
		mysql_real_escape_string($row['item_id']));
	$item_result = mysql_query($item_query);
	list($row['name']) = mysql_fetch_row($item_result);
	array_push($inventory,$row);
}
$smarty->assign('inventory',$inventory);
$smarty->assign('items',$items);
$smarty->display('item-shop.tpl');
 
?>

Extra Credit

  • Right now, we’re just displaying generic messages when a user buys an item. Change the messages so that they also tell the user what item they bought.
  • Add a box to the shop page that lets the user enter the quantity of the item they want to buy – so that users can buy 1 or more of any item.
  • Right now, our ’sell’ code is not very secured – a malicious user could simply pass in the ID of any item they wanted to sell that was in our game(whether it was in their inventory or not). Modify the item selling code so that it uses the ID of the row in user_items instead.
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