concept type hint in category php

This is an excerpt from Manning's book PHP in Action: Objects, Design, Agility. Login to get full access to this book.

Type hints are more likely to be useful in constructors than in other methods. Frequently, a constructor accepts an object as an argument, stores the object in an instance variable, and uses it later. A lot may happen between the time it’s inserted and the time the object is used; by checking the type when it’s passed into the constructor, we can get a possible error report much earlier, and it may be easier to find the bug.