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array_diff_key

PHP function Edit on GitHub ✎

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

Computes the difference of arrays using keys for comparison

Description

array_diff_key(array $array, array ...$arrays): array

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

Parameters

array: The array to compare from
arrays: Arrays to compare against

Return Values

Returns an array containing all the entries from array whose keys are absent from all of the other arrays.

Changelog

Version	Description

Examples

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

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

var_dump(array_diff_key($array1, $array2));
?>

The above example will output:

output

array(3) {
  ["blue"]=>
  int(1)
  ["red"]=>
  int(2)
  ["purple"]=>
  int(4)
}

php

<?php
$array1 = array('blue' => 1, 'red'  => 2, 'green' => 3, 'purple' => 4);
$array2 = array('green' => 5, 'yellow' => 7, 'cyan' => 8);
$array3 = array('blue' => 6, 'yellow' => 7, 'mauve' => 8);

var_dump(array_diff_key($array1, $array2, $array3));
?>

The above example will output:

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]);.