Laravel - Collections - Method Diff
The diff
method compares the collection against another collection or a plain PHP array
based on its values. This method will return the values in the original collection that are not present in the given collection:
$collection = collect([1, 2, 3, 4, 5]);
$diff = $collection->diff([2, 4, 6, 8]);
$diff->all();
// [1, 3, 5]
This method's behavior is modified when using Eloquent Collections.