array_intersect_assoc
array_intersect_uassoc
Array Functions
PHP Manual

# array_intersect_key

Computes the intersection of arrays using keys for comparison

### Description

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

array_intersect_key returns an array containing all the entries of `array1` which have keys that are present in all the arguments.

### Parameters

`array1`

  The array with master keys to check.

`array2`

  An array to compare keys against.

`...`

  A variable list of arrays to compare.

### Return Values

Returns an associative array containing all the entries of `array1` which have keys that are present in all arguments.

### Examples

Example #1 array_intersect_key example

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

The above example will output:

    array(2) {
      ["blue"]=>
      int(1)
      ["green"]=>
      int(3)
    }

In our example you see that only the keys 'blue' and 'green' are present in both arrays and thus returned. Also notice that the values for the keys 'blue' and 'green' differ between the two arrays. A match still occurs because only the keys are checked. The values returned are those of `array1`.

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.

### See Also

- array_diff
- array_udiff
- array_diff_assoc
- array_diff_uassoc
- array_udiff_assoc
- array_udiff_uassoc
- array_diff_key
- array_diff_ukey
- array_intersect
- array_intersect_assoc
- array_intersect_uassoc
- array_intersect_ukey