Question

What is the fastest/best way to create a function that retrieves a list of keys, that all contains a specific value in an array:

$array = ( 0 => 0,
           1 => 0,
           2 => 1,
           3 => 2,
           4 => 1 );

$keys= retrieve_keys_with_value( 1, $array );
var_dump($keys);
/* 
array(2) {
  [0] => int(2)
  [1] => int(4)
}
*/

Answer 1

$keys = array_keys($array, 1);

http://www.php.net/manual/en/function.array-keys.php

You may also want to pass the third parameter (strict checking). Default is false.

Remember. It’s PHP there is almost always a function for what you are doing 😉