"In the early days of PHP programming, PHP code was
limited to being procedural in nature. Procedural code is
characterized by the use of procedures for the building blocks of
the application. Procedures offer a certain level of reuse by
allowing procedures to be called by other procedures.
"However, without object-oriented language constructs, a
programmer can still introduce OO characteristics into PHP code.
It's a tad more difficult and can make the code more difficult to
read because it's mixing paradigms (procedural language with
pseudo-OO design). OO constructs in PHP code -- such as the ability
to define and use classes, the ability to build relationships
between classes that use inheritance, and the ability to define
interfaces -- make it much easier to build code that adheres to
good OO practices."