Array intersect on key in array?

Question

I have an array that has countries:

array(
'AF'=>'AFGHANISTAN',
'AL'=>'ALBANIA',
'DZ'=>'ALGERIA',
'AS'=>'AMERICAN SAMOA',
);

and I have another array that has some of the keys in it

array('AL', 'DZ');

I want to call a function that will take both arrays as parameters and return

array(
'AL'=>'ALBANIA',
'DZ'=>'ALGERIA',
);

I know php has built in functions to compare the keys, or the values, but it seems those functions all expect you to have two 1D arrays' or two 2D arrays.

I could loop over array_keys() for the first array and do a in_array() check on each key, but that seems really inefficent...

Answer 1

$selection = array('AL', 'DZ');
$filtered = array_intersect_key($countries, array_flip($selection));
var_dump($filtered);

Answer 2

Simply loop over the SECOND array, and fetch the values from the first. Vise versa seems unneeded inefficient indeed.

So:

$Arr1 = array(
'AF'=>'AFGHANISTAN',
'AL'=>'ALBANIA',
'DZ'=>'ALGERIA',
'AS'=>'AMERICAN SAMOA',
);

$Arr2 = array('AL', 'DZ');

$result = array();
foreach ($Arr2 as $cc){
  if (isset($Arr1[$cc])){
    $result[$cc] = $Arr1[$cc];
  }
}
print_r($result);

I don't think that is inefficient.

Edit addition: If you are 100% sure the $Arr2 contains only codes that can be found in $Arr1, you can of course skip the isset() test.