- print_r: documentation ( source)
- explode: documentation ( source)
- preg_replace: documentation ( source)
<?php
$hash = '8234jfr98j4fnui4hfj3289rj8';
$numbers = preg_replace('/[a-z]/si', 'a', $hash);
$numbers = explode('a', $numbers);
print_r($numbers);