Brian Haveri aka bwh2 | 31 December 2006
tutorial is an introduction to object oriented programming
(OOP) with PHP. Upon finishing this tutorial, you should
have the basic tools necessary to begin navigating the world
of OOP. Throughout, we will build upon one example while key
terms and nuances to OOP with PHP are introduced. In
addition, some time will be spent showing how to integrate
object oriented PHP with MySQL.
- Creating Our First Object
- Class Variables and Visibility
- Constructor Method
- Using Arrays to Speed Up Coding
- Method Interaction
- Integrating OO PHP with MySQL
- Introducing Inheritance
- Parting Words
- Now let's get started!
Not surprisingly, object oriented programming is focused
around objects. While the idea of objects may be foreign to
you in coding terms, understanding what objects are and why
we use them shouldn't take long. In short, our
non-programming world is comprised of objects. Computers,
fish, clouds, people, and cars are all objects. Objects have
properties like color, size, name, and speed. Objects can
also be comprised of other objects: cars have doors; doors
have handles; handles have plastic levers; so on and so
forth. Objects are everywhere around us. For this reason,
many programmers find object oriented programming relatively
easy to understand.
So how do objects translate into code? If we were building a
website about users, we would create one or many user
objects. Objects are created using classes. Classes are
groups of related variables and functions. Variables hold
our object's properties like color, size, and speed.
Functions perform actions like set variable values or open
files. In this example, we could create user objects with a
User class. You can think of the User class as a template
for any user objects.
Creating an object is called instantiation
(creating an instance). Let's instantiate a user object and
code the corresponding User class:
Note: As this tutorial
progresses, code will be removed so that you don't get lost
and can focus on the task at hand. Feel free to keep or add
back code from previous examples.
Right now this user can't do anything and doesn't have any
attributes. Within classes, we use methods (aka functions)
and variables to give our objects functionality and
properties. Let's redo our first example so that our users
can have a name:
As you can see, methods are declared using
function [methodName] format, as is standard in PHP. This
simple example shows us how we can apply a name to the
object, then access the name. Continue on to learn about how
we handle variables and methods within classes.
Note about PHP versions: If
you are running PHP4, the above code will not work for you.
Please continue on to the next section for an explanation.