- var_dump: documentation ( source)
- ctype_digit: documentation ( source)
- preg_match: documentation ( source)
<?php
var_dump(preg_match('/^-?\d+$/', new \stdClass()));
var_dump(preg_match('/^-?\d+$/', '123'));
var_dump(ctype_digit(0));
var_dump(ctype_digit("0"));
var_dump(ctype_digit("1"));