- preg_match: documentation ( source)
<?php
$raw = '<iframe src="http://embed.h2porn.com/gf-foreplay-pussy-licking/" frameborder="0" marginheight="0" marginwidth="0" scrolling="no" width="640" height="480"></iframe><br /><a href="http://h2porn.com/videos/gf-foreplay-pussy-licking/">GF Foreplay & Pussy Licking</a> brought to you by <a href="http://h2porn.com/">H2 Porn</a>';
preg_match('#\bsrc\="(\d+)"/#', $raw, $matches);
$embed = $matches[1];
echo $embed;