Computes the intersection of arrays using a callback function on the keys for comparison

# array_intersect_ukey

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

array_intersect_ukey — Computes the intersection of arrays using a callback function on the keys for comparison

### Description

array_intersect_ukey(array `$array`, array `...$arrays`, callable `$key_compare_func`): array

array_intersect_ukey() returns an array containing all the values of `array` which have matching keys that are present in all the arguments.

### Parameters

`array`

  Initial array for comparison of the arrays.

`arrays`

  Arrays to compare keys against.

`key_compare_func`

  The comparison function must return an integer less than, equal to, or greater than zero if the first argument is considered to be respectively less than, equal to, or greater than the second.

  callback(mixed `$a`, mixed `$b`): int
  Caution

  Returning non-integer values from the comparison function, such as float, will result in an internal cast to int of the callback's return value. So values such as `0.99` and `0.1` will both be cast to an integer value of `0`, which will compare such values as equal.

### Return Values

Returns the values of `array` whose keys exist in all the arguments.

### Examples

Example #1 array_intersect_ukey() example

`<?php
function key_compare_func($key1, $key2)
{
if ($key1 == $key2)
return 0;
else if ($key1 > $key2)
return 1;
else
return -1;
}
$array1 = array('blue' => 1, 'red' => 2, 'green' => 3, 'purple' => 4);
$array2 = array('green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan' => 8);
var_dump(array_intersect_ukey($array1, $array2, 'key_compare_func'));
?>`

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 `array`.

### 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_key() - Computes the difference of arrays using keys for comparison
- 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

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