How important is the order of arrays in the array_diff function in PHP?

The order of arrays in the array_diff function in PHP is important because it determines which array is considered the "base" array and from which the differences are calculated. The first array is considered the base array, and the function will return elements that are present in the base array but not in any of the other arrays. If the order of arrays is switched, the result of the array_diff function will also be different. To ensure the correct behavior of array_diff, always make sure to place the base array as the first argument in the function call.

$array1 = [1, 2, 3, 4, 5];
$array2 = [3, 4, 5];
$array3 = [1, 2];

// Correct order of arrays
$diff = array_diff($array1, $array2, $array3);
print_r($diff);

// Incorrect order of arrays
$diff = array_diff($array2, $array1, $array3);
print_r($diff);