Let's say I have an object - a User object in this case - and I'd like to be able to track changes to with a separate class. The User object should not have to change it's behavior in any way for this to happen.

Therefore, my separate class creates a "clean" copy of it, stores it somewhere locally, and then later can compare the User object to the original version to see if anything changed during its lifespan.

Is there a function, a pattern, or anything that can quickly compare the two versions of the User object?

Option 1 Maybe I could serialize each version, and directly compare, or hash them and compare?

Option 2 Maybe I should simply create a ReflectionClass, run through each of the properties of the class and see if the two versions have the same property values?

Option 3 Maybe there is a simple native function like objects_are_equal($object1,$object2);?

What's the fastest way to do this?