In this chapter, we have looked at object-oriented programming, a powerful way to closely couple data and operations on them by defining new classes of types in your scripts. Through this, we can declare these classes as having properties and methods.
The OOP features in PHP5 are powerful enough that in addition to creating classes of objects, we can extend them and create entire hierarchies of related types. We also saw how we can use interfaces to describe functionality that others can then incorporate into their own classes.
In the next chapter, we will turn our attention back to arrays, a powerful data type in PHP that deserves more attention.