The array_diff_key Function

The array_diff_key function compares the keys of two or more arrays and returns an array containing the elements from the first array whose keys are not present in the other arrays. The comparison is based only on keys; the values of the elements are not taken into account.

Syntax

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

Example

Let's compare two arrays by keys:

<?php
	$arr1 = ['a' => 1, 'b' => 2, 'c' => 3];
	$arr2 = ['a' => 4, 'd' => 5];
	
	$res = array_diff_key($arr1, $arr2);
	print_r($res);
?>

Code execution result:

['b' => 2, 'c' => 3]

Example

Comparing three arrays by keys:

<?php
	$arr1 = [1 => 'a', 2 => 'b', 3 => 'c'];
	$arr2 = [1 => 'd', 4 => 'e'];
	$arr3 = [5 => 'f', 2 => 'g'];
	
	$res = array_diff_key($arr1, $arr2, $arr3);
	print_r($res);
?>

Code execution result:

[3 => 'c']

Example

Using numeric and string keys:

<?php
	$arr1 = ['color' => 'red', 1 => 'a', 2 => 'b'];
	$arr2 = [1 => 'c', 'size' => 'XL'];
	
	$res = array_diff_key($arr1, $arr2);
	print_r($res);
?>

Code execution result:

['color' => 'red', 2 => 'b']

The array_diff_key Function

Syntax

Example

Example

Example

See Also