Laravel - Collections - Method Diff
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.