- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$_content = '<iframe frameborder="0" width="480" height="270" src="//www.dailymotion.com/embed/video/x248ctr" allowfullscreen></iframe><br /><a href="http://www.dailymotion.com/video/x248ctr_logitech-g402-hyperion-fury-gaming-mouse-inhumanly-fast_tech" target="_blank">Logitech G402 Hyperion Fury Gaming Mouse...</a> <i>by <a href="http://www.dailymotion.com/LinusTechTips" target="_blank">LinusTechTips</a></i>';
preg_match('#dailymotion.com\/(?:embed\/video|swf\/video|video)\/([^\'"\/\?_]+)#i',$_content, $matches);
var_dump($matches);
echo $_content;