Opposite of array_intersect?

Question

Is there a built-in function to get all members of array 1 which do not exist in array 2?
I know how to do it programatically, only wondering if there is a built-in function

Answer 1

array_diff is definitely the obvious choice but it is not technically the opposite of array interesect. Take this example:

$arr1 = array('rabbit','cat','dog');

$arr2 = array('cat','dog','bird');

print_r( array_diff($arr1, $arr2) );

What you want is a result with 'rabbit' and 'bird' in it but what you get is only rabbit because it is looking for what is in the first array but not the second (and not vice versa). to truly get the result you want you must do something like this:

$arr1 = array('rabbit','cat','dog');

$arr2 = array('cat','dog','bird');

$diff1 = array_diff($arr1, $arr2);
$diff2 = array_diff($arr2, $arr1);
print_r( array_merge($diff1, $diff2) );

Note: This method will only work on arrays with numeric keys.