array_diff_key

(PHP 5 >= 5.1.0, PHP 7)

array_diff_key — 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.

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, 'yellow' => 7, 'cyan' => 8);

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

The above example will output:

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

<?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:

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() - Computes the difference of arrays
  • array_udiff() - Computes the difference of arrays by using a callback function for data comparison
  • array_diff_assoc() - Computes the difference of arrays with additional index check
  • array_diff_uassoc() - Computes the difference of arrays with additional index check which is performed by a user supplied callback function
  • array_udiff_assoc() - Computes the difference of arrays with additional index check, compares data by a callback function
  • array_udiff_uassoc() - Computes the difference of arrays with additional index check, compares data and indexes by a callback function
  • array_diff_ukey() - Computes the difference of arrays using a callback function on the keys for comparison
  • array_intersect() - Computes the intersection of arrays
  • array_intersect_assoc() - Computes the intersection of arrays with additional index check
  • array_intersect_uassoc() - Computes the intersection of arrays with additional index check, compares indexes by a callback function
  • array_intersect_key() - Computes the intersection of arrays using keys for comparison
  • array_intersect_ukey() - Computes the intersection of arrays using a callback function on the keys for comparison

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https://www.php.net/manual/en/function.array-diff-key.php