- var_dump: documentation ( source)
- preg_replace: documentation ( source)
<?php
$text = "[quote=foo]<script src='http://www.example.com' data-junk='[/quote]'>";
$text = preg_replace('#\[quote\=(.+)\]((?>(?R)|.)+)\[\/quote\]#iUs', '<div class="quote">$2</div><div class="quote-by">By: $1</div>', $text, -1, $count);
var_dump($text);