- print_r: documentation ( source)
- explode: documentation ( source)
- preg_grep: documentation ( source)
<?php
$words = "systematic,gear,synthesis,mysterious,system,mine,elabrate,along,sympathy";
$words=explode(",",$words);
$your_array = preg_grep("/^(^s|^m|^e)/", $words);
print_r($your_array);