Edd Mann Developer

Handling Array Equality in PHP

If you want to check if two arrays contain the same values, regardless of order, you will have some issue using the operators == and ===.

With the equal operator == you are able to check for equality based on the type coerced values and keys (regardless of order).

<?php
[1, 2, 3] == [1, 2, 3] // true
[1, 2, 3] == [1, 2, '3'] // true
[1, 2, 3] == [1, 3, 2] // false
[1, 2, 3] == [0 => 1, '2' => 3, 1 => 2] // true

With the identical operator === you are able to check for equality based on the type and exact ordering of the keys.

<?php
[1, 2, 3] === [1, 2, 3] // true
[1, 2, 3] === [1, 2, '3'] // false
[1, 2, 3] === [1, 3, 2] // false
[1, 2, 3] === [0 => 1, 2 => 3, 1 => 2] // false

This is not always what you desire, treating the collection as a Set, you do not wish to validate the position of the element, only its’ presence. However, this can be resolved by using the following functions.

<?php
function array_values_equal($a, $b) {
    $x = array_values($a);
    $y = array_values($b);

    sort($x);
    sort($y);

    return $x == $y;
}

function array_values_identical($a, $b) {
    $x = array_values($a);
    $y = array_values($b);

    sort($x);
    sort($y);

    return $x === $y;
}

array_values_equal(['1', 2, 3], [3, 2, 1]) // true
array_values_identical([1, 2, 3], [3, 2, 1]) // true