- var_dump: documentation ( source)
- array_search: documentation ( source)
<?php
$array = array(
array("id" => 1, "value" => 1),
array("id" => 2, "value" => null),
array("id" => 3, "value" => 3),
array("id" => 4, "value" => 4),
array("id" => 5, "value" => 5),
array("id" => 6, "value" => 6)
);
var_dump(array_search(null, $array));