- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$_content = '[iframe scrolling="no" src="https://w.soundcloud.com/player/?url=https%3A//api.soundcloud.com/tracks/163969592&color=ff5500&auto_play=false&hide_related=false&show_comments=true&show_user=true&show_reposts=false" frameborder="no" height="166" width="100%"]';
if(preg_match('#[<\[](iframe [^>\]]*?(soundcloud.com|youtu|vimeo)[^>\]]*?)[>\]]#i', $_content, $matches) > 0) var_dump($matches);