array_diff

(PHP 4 >= 4.0.1, PHP 5, PHP 7)

Computes the difference of arrays

array array_diff ( array $array1, array $array2 [, array $... ] )

Compares array1 against one or more other arrays and returns the values in array1 that are not present in any of the other arrays.

Parameters:

array1

The array to compare from

array2

An array to compare against

...

More arrays to compare against

Returns:

Returns an array containing all the entries from array1 that are not present in any of the other arrays.

Notes:

Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. In words: when the string representation is the same.

This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff($array1[0], $array2[0]);.

Examples:

array_diff() example

<?php
$array1 = array("a" => "green", "red", "blue", "red");
$array2 = array("b" => "green", "yellow", "red");
$result = array_diff($array1, $array2);
 
print_r($result);
?>

Multiple occurrences in $array1 are all treated the same way. This will output :

Array
(
    [1] => blue
)