- var_dump: documentation ( source)
- array_search: documentation ( source)
- array_flip: documentation ( source)
<?php
var_dump(array_search('pizza', array_flip(array('pizza' => 'pie', 'mushroom' => 'salsa'))));
var_dump(array_search('onions', array_flip(array('pizza' => 'pie', 'mushroom' => 'salsa'))));