Building Browsergames » items 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 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 Dropping Items (PHP) http://buildingbrowsergames.com/2008/10/22/dropping-items-php/ http://buildingbrowsergames.com/2008/10/22/dropping-items-php/#comments Wed, 22 Oct 2008 14:00:33 +0000 Luke http://buildingbrowsergames.com/?p=514 Now that we’ve created a way for users to buy items, we need to create a way for users to get items without buying them – like from monsters they kill in combat. Today, we will be adding item drops to our combat system.

To start off, check out a recent copy of our code:

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

First things first, we need to add a 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)
);

We will be using this monster_items table to keep track of the items that users can gain after combat. The monster_id and item_id columns are fairly self-explanatory; the one column that might need some explaining is the rarity column. We will be using this column to determine how frequently different items drop from our monsters – for example, if we put a Sword into our monster_items table, with a rarity of 10, it would have a 10% chance of dropping any time that the monster it was linked to was killed. As you can see, we will be using the rarity column to define the chance of an item dropping.

With our database preparations made, let’s move on to writing some code. First, open up forest.tpl:

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<p>You found a <strong>{$item}</strong>!</p>

We will be using that brief addition to display to the user the new item that they just found. Now that we’ve modified our template, let’s make some changes to what happens when a player wins a fight:

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$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);

Most of this code is the same code as we used to add items to the player’s inventory in our item shop from earlier. However, the first 5 lines are what we’re really interested in: they are how we retrieve the random item that the player should receive. First, we generate a value between 0 and 100 – this will be the ‘rarity barrier’. We use the number that we generated to choose items from the monster’s drop table, which have a rarity greater than or equal to our random number. For example, if we were to generate the number 20, any items with a rarity of 20 or greater would be available for the player to win as a result of their combat. Once we’ve retrieved a random item for the player, we add it to their inventory – and that’s that. You’ve seen everything else we do in this code before.

Here’s the new forest.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);				
		} 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 {
	$query = sprintf("SELECT name FROM monsters ORDER BY RAND() LIMIT 1");
	$result = mysql_query($query);
	list($monster) = mysql_fetch_row($result);
	$smarty->assign('monster',$monster);
}
 
$smarty->display('forest.tpl');
 
?>

Extra Credit

  • As I mentioned, we’re duplicating code here – which is bad. Can you DRY out the code to add an item to a player’s inventory?
]]> http://buildingbrowsergames.com/2008/10/22/dropping-items-php/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.
]]> http://buildingbrowsergames.com/2008/10/13/buying-items/feed/ 0 Preparing our items system http://buildingbrowsergames.com/2008/10/10/preparing-our-items-system/ http://buildingbrowsergames.com/2008/10/10/preparing-our-items-system/#comments Fri, 10 Oct 2008 14:00:07 +0000 Luke http://buildingbrowsergames.com/?p=478 If you’ve been keeping track of our design document from earlier at all, you may have noticed that we are starting to come close to finishing our game. There are still a few features left to refine and tweak, and a few more left to implement – but we’re getting closer. Today, we’ll be laying the groundwork for our items and inventory system – and on monday, we’ll dig into actually implementing it.

Because we want to be able to perform whatever actions we want on a player, we’re going to need a way to flag our items – to say “this is a healing potion”, “this item teleports the user”, and so on. To that end, we’ll add another stat to our stats table:

INSERT INTO stats(display_name,short_name) VALUES ('Item Use Token','token');

We will be using the value of the ‘token’ stat on our items to determine what exactly we should be doing with our items when we use them.

We will also need to add another table to our database – to keep track of the items in the player’s inventory. We’ll create user_items like so:

CREATE TABLE user_items (
	id int NOT NULL AUTO_INCREMENT,
	user_id int NOT NULL,
	item_id int NOT NULL,
	quantity int NOT NULL DEFAULT 0,
	PRIMARY KEY(id)
);

And with that finished, we’re all set! All we’ve got to do is write the code, now – which we’ll do on monday. See you then!

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