what is the function of array_diff in PHP?

`array_diff()` is a PHP array function used to compare two or more arrays and return the values that are present in one array but not in the other arrays.

In specific terms, the `array_diff()` function compares the values in the first array with the values in all other arrays and returns only the values that appear in the first array but not in the other arrays. The result is a new array containing the values that make up the difference.

Here is an example of using the `array_diff()` function:

$array1 = [1, 2, 3, 4, 5];
$array2 = [2, 4, 6];
$result = array_diff($array1, $array2);
print_r($result);

The output result is:

Array
(
    [0] => 1
    [2] => 3
    [4] => 5
)

In the example, `$array1` and `$array2` are two arrays. `array_diff($array1, $array2)` compares these two arrays and returns the values that appear only in `$array1` and not in `$array2`. Therefore, the output is a new array containing the set difference.