Фильтруем массив по значениям

array_filter_by_values.php

<?
$rows = array('a' => 1, 'b' => 2);
$f = array(2 => true);

function array_filter_by_values($_rows, $_filter_keys) {
    $filter = function($key) use ($_filter_keys) {return isset($_filter_keys[$key]) && $_filter_keys[$key];};
    $out = array_filter($_rows, $filter);
    return $out;
}

$t = array_filter_by_values($rows, $f);
var_dump($t);

// array(1) {
//   ["b"]=>
//   int(2)
// }