- var_dump: documentation ( source)
- filter_var: documentation ( source)
<?php
var_dump(filter_var('true', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('1', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('false', FILTER_VALIDATE_BOOLEAN));
var_dump(filter_var('0', FILTER_VALIDATE_BOOLEAN));