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.

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User Contributed Notes 2 notes

down

lincoln dot du dot j at gmail dot com ¶

2 months ago

This is a cleaner and more modern approach (PHP 7.4+ syntax).

<?php

$array1 = ['blue' => 1, 'red' => 2, 'green' => 3, 'purple' => 4];
$array2 = ['green' => 5, 'blue' => 6, 'yellow' => 7, 'cyan' => 8];

$result = array_intersect_ukey($array1, $array2, fn($a, $b) => $a <=> $b);

var_dump($result);

?>

Explanation:
The comparison function fn($a, $b) => $a <=> $b uses the spaceship operator directly inside the array_intersect_ukey call.

The result will contain entries from $array1 whose keys also exist in $array2.

Output:
php
Copy
Edit
array(2) {
 ["blue"]=>
 int(1)
 ["green"]=>
 int(3)
}