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# array_intersect_key

(PHP 5 >= 5.1.0RC1)

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 values of `array1` which have matching keys that are present in all the arguments.

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() and array_intersect_ukey().

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