Note that the order of the keys in the returned array is the same as the order of the keys in the source array. eg:
<?php
$array = array(
'two' => 'a',
'three' => 'b',
'one' => 'c',
);
$keyswant = array(
'one' => '',
'three' => '',
);
print_r(array_intersect_key($array, $keyswant));
?>
Shows:
Array
(
[three] => b
[one] => c
)