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Computes the difference of arrays using keys for comparison (PHP 5 >= 5.1.0)
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.



The array to compare from


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.


Example 239. 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.

= 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) {



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]);.