What is the function array_diff() used for in PHP and how can it be applied to multidimensional arrays?

The function array_diff() in PHP is used to compute the difference between arrays. It returns an array containing all the values from array1 that are not present in any of the other arrays provided as arguments. To apply array_diff() to multidimensional arrays, you can use a combination of array_map() and array_diff() to compare the subarrays. 

$array1 = array(
    array("a" => "green", "b" => "brown", "c" => "blue", "d" => "yellow"),
    array("e" => "purple", "f" => "orange", "g" => "pink", "h" => "red")
);

$array2 = array(
    array("a" => "green", "b" => "brown", "c" => "blue"),
    array("e" => "purple", "f" => "orange")
);

$diff = array_map(function($a, $b) {
    return array_diff($a, $b);
}, $array1, $array2);

print_r($diff);

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