# array_diff_key

(PHP 5 >= 5.1.0)

array_diff_key — Computes the difference of arrays using keys for comparison

### Description

array array_diff_key ( array `$array1` , array `$array2` [, array `$...` ] )

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.

### Parameters

`array1`

  The array to compare from

`array2`

  An array to compare against

`...`

  More arrays to compare against

### Return Values

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

### Examples

Example#1 array_diff_key() example

The two keys from the key => value pairs are considered equal only if (string) $key1 === (string) $key2 . In other words a strict type check is executed so the string representation must be the same.

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

The above example will output:

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

### Notes

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

### See Also

- array_diff()
- array_udiff()
- array_diff_assoc()
- array_diff_uassoc()
- array_udiff_assoc()
- array_udiff_uassoc()
- array_diff_ukey()
- array_intersect()
- array_intersect_assoc()
- array_intersect_uassoc()
- array_intersect_key()
- array_intersect_ukey()