array_diff

Again, the function's description is misleading right now. I sought a function, which (mathematically) computes A - B, or, written differently, A \ B. Or, again in other words, suppose 

A := {a1, ..., an} and B:= {a1, b1, ... , bm}

=> array_diff(A,B) = {a2, ..., an}

array_diff(A,B) returns all elements from A, which are not elements of B (= A without B).

You should include this in the documentation more precisely, I think.

array_diff provides a handy way of deleting array elements by their value, without having to unset it by key, through a lengthy foreach loop and then having to rekey the array.

<?php

//pass value you wish to delete and the array to delete from
function array_delete( $value, $array)
{
    $array = array_diff( $array, array($value) );
    return $array;
}
?>

The description is kinda ambiguous at first glance, one might think that the array_diff function returns the differences across *all* given arrays (which is what I was actually looking for, and that's why I was surprised that, in the example code, the result did not include "yellow").

However, i wrote a neat oneliner to compute the differences across all given arrays:

<?php
# Returns an array with values that are unique across all of the given arrays
function array_unique_values(...$arrays) {
    return array_keys(array_filter(array_count_values(array_merge(...$arrays)), fn($count) => $count === 1));
}

# Example:
$array1 = ['a', 'b', 'c', 'd'];
$array2 = ['a', 'b', 'x', 'y'];
$array3 = ['a', '1', 'y', 'z'];

print_r(array_unique_values($array1, $array2, $array3));
?>

Result:
Array
(
    [0] => c
    [1] => d
    [2] => x
    [3] => 1
    [4] => z
)

If you want a simple way to show values that are in either array, but not both, you can use this:

<?php
function arrayDiff($A, $B) {
    $intersect = array_intersect($A, $B);
    return array_merge(array_diff($A, $intersect), array_diff($B, $intersect));
}
?>

If you want to account for keys, use array_diff_assoc() instead; and if you want to remove empty values, use array_filter().

<?php
/**
   * Check If An Array Is A Subset Of Another Array
   *
   * @param  array $subset
   * @param  array $set
   * @return bool
   */
function is_subset(array $subset, array $set): bool {
     return (bool)!array_diff($subset, $set);
}

$u = [1, 5, 6, 8, 10];
$a = [1, 5];
$b = [6, 7];

var_dump(is_subset($a, $u)); // true
var_dump(is_subset($b, $u)); // false

Hello guys,

I´ve been looking for a array_diff that works with recursive arrays, I´ve tried the ottodenn at gmail dot com function but to my case it doesn´t worked as expected, so I made my own. I´ve haven´t tested this extensively, but I´ll explain my scenario, and this works great at that case :D

We got 2 arrays like these:

<?php
$aArray1['marcie'] = array('banana' => 1, 'orange' => 1, 'pasta' => 1);
$aArray1['kenji'] = array('apple' => 1, 'pie' => 1, 'pasta' => 1);

$aArray2['marcie'] = array('banana' => 1, 'orange' => 1);
?>

As array_diff, this function returns all the items that is in aArray1 and IS NOT at aArray2, so the result we should expect is:

<?php
$aDiff['marcie'] = array('pasta' => 1);
$aDiff['kenji'] = array('apple' => 1, 'pie' => 1, 'pasta' => 1);
?>

Ok, now some comments about this function:
 - Different from the PHP array_diff, this function DON´T uses the === operator, but the ==, so 0 is equal to '0' or false, but this can be changed with no impacts.
 - This function checks the keys of the arrays, array_diff only compares the values.

I realy hopes that this could help some1 as I´ve been helped a lot with some users experiences. (Just please double check if it would work for your case, as I sad I just tested to a scenario like the one I exposed)

<?php
function arrayRecursiveDiff($aArray1, $aArray2) {
    $aReturn = array();
   
    foreach ($aArray1 as $mKey => $mValue) {
        if (array_key_exists($mKey, $aArray2)) {
            if (is_array($mValue)) {
                $aRecursiveDiff = arrayRecursiveDiff($mValue, $aArray2[$mKey]);
                if (count($aRecursiveDiff)) { $aReturn[$mKey] = $aRecursiveDiff; }
            } else {
                if ($mValue != $aArray2[$mKey]) {
                    $aReturn[$mKey] = $mValue;
                }
            }
        } else {
            $aReturn[$mKey] = $mValue;
        }
    }
   
    return $aReturn;
}
?>

If you just need to know if two arrays' values are exactly the same (regardless of keys and order), then instead of using array_diff, this is a simple method:

<?php

function identical_values( $arrayA , $arrayB ) {

    sort( $arrayA );
    sort( $arrayB );

    return $arrayA == $arrayB;
}

// Examples:

$array1 = array( "red" , "green" , "blue" );
$array2 = array( "green" , "red" , "blue" );
$array3 = array( "red" , "green" , "blue" , "yellow" );
$array4 = array( "red" , "yellow" , "blue"