Answer by Petr Cibulka for How to check if multiple array keys exists

It seems to me, that the easiest method by far would be this:

$required = array('a','b','c','d');$values = array('a' => '1','b' => '2');$missing = array_diff_key(array_flip($required), $values);

Prints:

Array(    [c] => 2    [d] => 3)

This also allows to check which keys are missing exactly. This might be useful for error handling.