- var_dump: documentation ( source)
- vsprintf: documentation ( source)
- preg_match_all: documentation ( source)
<?php
preg_match_all('/^([a-z]{0,3})(\d{3})[-\s]?(\d{2})[-\s]?(\d{4})([0-9a-z]{0,3})$/i', 'ABC123121234ABC', $number);
var_dump($number);
var_dump(vsprintf('%2$s%3$s-%4$s-%5$s%6$s', $number));