The array_diff() function returns an array of elements that exist in one array but not in any other arrays to which it is compared. code example

Example: array_diff

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

Array
(
    [1] => blue
)