- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
$enclosure = 'http://www.somesite.com/path1/path2/path3/somefile.150x150.png.jpg?size=150';
$pattern = '#(\.(png|jpg|jpeg|jpe|gif|tif|tiff|svg|ico|icon|x-icon)[\?]+)$+#i';
preg_match($pattern,$enclosure,$matches);
var_dump($matches);