- var_dump: documentation ( source)
- preg_match: documentation ( source)
- strspn: documentation ( source)
<?php
$digits = '1234567890';
$alnum = '123test';
var_dump(preg_match('/^\d+$/D', $digits));
var_dump(preg_match('/^\d+$/D', $alnum));
var_dump(strspn($digits, $digits) === strlen($digits));
var_dump(strspn($alnum, $digits) === strlen($alnum));