- explode: documentation ( source)
- in_array: documentation ( source)
- strtolower: documentation ( source)
- array_pop: documentation ( source)
<?php
$exclude_exts = array('js', 'css',);
$filename = "test.css";
$is_excluded = in_array(strtolower(array_pop(explode('.',$filename))), $exclude_exts);