array_diff_ukey

(PHP 5 >= 5.1.0, PHP 7)

Computes the difference of arrays using a callback function on the keys for comparison

array array_diff_ukey ( array $array1, array $array2 [, array $... ], callable $key_compare_func )

Compares the keys from array1 against the keys from array2 and returns the difference. This function is like array_diff() except the comparison is done on the keys instead of the values.

Unlike array_diff_key() a user supplied callback function is used for the indices comparison, not internal function.

Parameters:

array1

The array to compare from

array2

An array to compare against

...

More arrays to compare against

key_compare_func

The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

int callback ( mixed $a, mixed $b )

Returns:

Returns an array containing all the entries from array1 that are not present in any of the other arrays.

Notes:

This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff_ukey($array1[0], $array2[0], 'callback_func');.

Examples:

array_diff_ukey() example

<?php
function key_compare_func($key1, $key2)
{
    if ($key1 == $key2)
        return 0;
    else if ($key1 > $key2)
        return 1;
    else
        return -1;
}

$array1 = array('blue'  => 1, 'red'  => 2, 'green'  => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan'   => 8);

var_dump(array_diff_ukey($array1, $array2, 'key_compare_func'));
?>

The above example will output:

array(2) {
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}