This is probably the most misunderstood PHP concept for people coming from other languages. A reference and a value are two completely different things. A reference is a memory address. A value can be of any type. Using the same terminology as we use for different types of pointers in C, here is how to distinguish between a reference and a value: -A ___ reference to an object is just a memory address (int). -A ___ object's value can be of any type (string, array, boolean, resource, etc.).