- print_r: documentation ( source)
- explode: documentation ( source)
- preg_grep: documentation ( source)
<?php
$words = "systematic,gear,synthesis,mysterious";
$words=explode(",",$words);
$res = preg_grep('~(?=[^s]*s)(?=[^m]*m)(?=[^e]*e)~', $words);
print_r($res);