get an array that does not exist in another array

Question

for example I have 2 arrays like the following:

array1 = (2, 3, 4);
array2 = (1, 2, 3, 4, 5);

I want to get the value of the second array, where the value array1 is not found in array2, so we can conclude the following are array3

array3 = (1, 5);

Answer 1

$array3 = array_diff($array1, $array2);

Answer 2

Diff the arrays

$array3 = array_diff($array2, $array1);