Remove Array Elements Based on Key

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
);

What have you tried? We are happy to help you fix problems in your existing code, but we will not (in most cases) write the code for you. — George Cummins
– George Cummins, Commented Mar 5, 2012 at 21:46

gen_Eric · Accepted Answer · 2012-03-05 21:47:32Z

3

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));

answered Mar 5, 2012 at 21:47

gen_Eric

228k42 gold badges304 silver badges343 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

This will not preserve the values from $array1. The result is Array ( [1] => 0 [4] => 1 ).

@GeorgeCummins: I fixed it. I had the parameters reversed. It works correctly now :-)

Shiplu Mokaddim · Accepted Answer · 2012-03-05 21:55:03Z

1

Use array_intersect_key with array_flip,

$r = array_intersect_key($a, array_flip($b));

answered Mar 5, 2012 at 21:55

Shiplu Mokaddim

57.5k20 gold badges147 silver badges193 bronze badges