- var_dump: documentation ( source)
- implode: documentation ( source)
- preg_replace: documentation ( source)
- str_split: documentation ( source)
<?php
$mac = '00:11:22:33:44:55';
$input = '233';
$regex = '('. implode(':*', str_split($input)) .')';
$mac = preg_replace('/'. $regex .'/', '<b>$1</b>', $mac);
var_dump($mac);