- substr: documentation ( source)
- strrpos: documentation ( source)
<?php
$files['beam/email_header.jpg'] = "/u01/foo/bar/baz/_base/beam/email_header.jpg";
echo substr($files['beam/email_header.jpg'],strrpos($files['beam/email_header.jpg'],'/',((strlen('/beam/email_header.jpg')*-1)-1)));