Arguments are like this:
function foo(arr1, arr2, arr3, arr4 ...)
and the function should return a array of all elements from arr2, arr3, arr4 ... that don't exist in arr1.
Is there a built in function for this? Or do I need to make it myself with foreach and stuff? :)
There is no built-in function that does exactly what you are asking for. array_diff() is close, but not quite. So you'll have to roll your own nice neat function or else do something ugly like this:
array_diff( array_unique(
array_merge(
array_values($arr2),
array_values($arr3),
array_values($arr4)
)),
$arr1
);
You can remove the call to array_unique() if you want values that appear multiple times in the arrays to also be represented multiple times in your result.
You can remove the calls to array_values() if your keys in your arrays are all numeric or if you are certain that there are no non-numeric keys that appear in more than one of the arrays being merged.
So, in those ideal circumstances, it can be simplified to:
array_diff( array_merge( $arr2, $arr3, $arr4 ), $arr1 );
You can do this with array_diff, but you'll have to turn things around a bit.
$result = array_diff (array_merge ($arr2, $arr3, $arr4), $arr1);
EDIT: Trott's answer covers a load of edge cases that mine doesn't. That's probably the best solution you're going to get.
