Here you go, as promised 
PHP Code:
<?php
if (isset($_POST["getPlayers"])) {
if (!$_POST["world"])
echo "Please enter world number";
else {
$world = $_POST["world"];
$data = file_get_contents("http://www.runescape.com/slu.ws?order=WMLPA");
$search = strstr($data, "World {$world}");
$players = substr($search, 21 + strlen($world), 4);
$players = trim($players);
$players = (is_numeric($players) ? $players : 2000);
echo $players." players";
}
}
print <<<EOD
<form action="" method="post">
<label for="world">World:</label>
<input type="text" name="world" value="{$_POST["world"]}" />
<input type="submit" name="getPlayers" value="Get Players" />
</form>
EOD;
?>
~NS