Question

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? 🙂

Answer 1

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 );