Get the TF2 backpack of a user. Proof of concept - no backpack or schema caching added yet. Adapted from http://wiki.teamfortress.com/wiki/Talk:WebAPI/GetPlayerItems

backpack.php

<?php
    
  $APIkey = 'API KEY HERE'; // Use your own API key here
	$profile = $_GET['id']; // usage: page.php?id=1234567890
	if (empty($profile))
    {
        exit(0);
    }
	// Put together the URL for the backpack
	$backpackURL = "http://api.steampowered.com/IEconItems_440/GetPlayerItems/v0001/?key=" . $APIkey . "&SteamID=" . $profile . "&format=json";
	
    $schemaURL = "http://api.steampowered.com/IEconItems_440/GetSchema/v0001/?key=" . $APIkey . "&language=en";
    
	// Download and decode the json file
	$userBackpack = json_decode(file_get_contents($backpackURL), true);
	$itemSchema = json_decode(file_get_contents($schemaURL), true);
    
	$backpack_items = $userBackpack['result'];
	$schema_items = $itemSchema['result'];
    
	// Iterate through each item
	foreach($backpack_items['items'] as $ind=>$backpack_items) {
		// Store all of the item's information in separate variables
		$id =  $backpack_items['id'];
		$defindex = $backpack_items['defindex'];
        $image_url = "";
        $name = getItemName($schema_items, $defindex, $image_url);
		$level = $backpack_items['level'];
		$quantity = $backpack_items['quantity'];
		$flag_cannot_trade = (array_key_exists('flag_cannot_trade', $backpack_items) ? $backpack_items['flag_cannot_trade'] : false); 
		$inventory = $backpack_items['inventory']; // The inventory value is stored just like all of the others
		$position = $inventory & 65535; // You can directly perform bitwise operations on the value. PHP understands that you mean this to be a number
		$equipped = ($inventory >> 16) & 1023; // More bitwise operations to get the equipped number
		$equippedString = getEquipped($equipped); // Convert the equipped number into a string
		$quality = $backpack_items['quality'];
        $quality = getQuality($quality);
		
		// Print out everything. It's ugly, but it does the job.
		echo "
            <img src=$image_url /><br/>
            Name: ";
            if($quality != "Unique"){ echo $quality . " "; } 
        echo "$name <br/>
            ID: $id <br/>
            Defindex: $defindex <br/>
            Level: $level <br/>
            Quantity: $quantity <br/>
            Cannot trade: $flag_cannot_trade <br/>
            Inventory: $inventory <br/>
            Position: $position <br/>
            Equipped: $equipped - $equippedString <br/>
            Quality: $quality<br/>";
	}
	
    function getQuality($quality)
    {
        if ($quality == 1)
            return "Genuine";
        if ($quality == 3)
            return "Vintage";
        if ($quality == 5)
            return "Unusual";
        if ($quality == 6)
            return "Unique";
        if ($quality == 7)
            return "Community";
        if ($quality == 9)
            return "Self-Made";
        if ($quality == 11)
            return "Strange";
        if ($quality == 13)
            return "Haunted";
        return "";
    }
    
    function getItemName($schema, $defindex, &$image_url)
    {
        $itemName = "";
        foreach($schema['items'] as $ind=>$schema) {
            // Store all of the item's information in separate variables
            $schema_defindex = $schema['defindex'];            
            if ($defindex == $schema_defindex)
            {
                $itemName = $schema['item_name'];
                // we pass in image_url variable as a reference so we can make changes to it while we look up the item name
                $image_url = $schema['image_url'];
            }
        }
        return $itemName;
    }
    
	function getEquipped($equipNumber) {
		// Create an array with all of the classes in the proper order
		$classList = array(0=>'Scout', 'Sniper', 'Soldier', 'Demoman', 'Medic', 'Heavy', 'Pyro', 'Spy', 'Engineer');
		// Start with an empty string
		$equippedString = '';
		for ($i = 0; $i < 10; $i++) {
			if ((1<<$i) & $equipNumber) { // Check that the class's bit appears in the number
				if ($equippedString)
					$equippedString .= ', '; // If the string is not empty, add a comma
					
				$equippedString .= $classList[$i]; // Add the name of the class to the string if it is equipped by that class
			}
		}
		if (!$equippedString)
			$equippedString = 'None'; // The string is "None" if no one has it equipped
		return $equippedString; 
	}	
?>