Question

I have an array:

array(
  '1' => red,
  '2' => green,
  '3' => blue,
  '4' => orange
);

And a second array:

array(
  '0' => 1,
  '1' => 4
);

I want to keep only those elements in Array 1 that have a key value equal to a value in Array 2.

So the final array should look like:

array (
    '1' => red,
    '4' => orange
);

Answer 1

Use array_intersect_key to get the values that share keys (after using array_flip on the 2nd array).

$array3 = array_intersect_key($array1, array_flip($array2));