PHP ile URL den bir kısmını alma, Nasıl?

<?php
$url = 'http://www.play4me.com/game/play.php?g=41455466448&s=boyz&k=18';
preg_match('"http://www.play4me.com/game/play.php?g=([0-9]+)"', $url, $id);
echo $id[1];
?>

explode ile;
<?
$ref = "http://www.play4me.com/game/play.php?g=41455466448";
$a = explode("g=", $ref);
$ref = $a[1];
echo $ref;
?>