- array_intersect_key: documentation ( source)
- print_r: documentation ( source)
- array_flip: documentation ( source)
<?php
$a = array('x' => 1, 'y' => 2, 'z' => 3, 'a' => 4, 'b' => 4);
$b = array('x', 'z', 'a');
$result = array_intersect_key($a, array_flip($b));
print_r($result);