3.2 OBJECTS
The main difference in OOP as opposed to functional programming is that the
data and code are bundled together into one entity, which is known as an
object. Object-oriented applications are usually split up into a number of
objects that interact with each other. Each object is usually an entity of the
problem, which is self-contained and has a bunch of properties and methods.
The properties are the object’s data, which basically means the variables that
belong to the object. The methods–if you are coming from a functional back-
ground–are basically the functions that the object supports. Going one step
further, the functionality that is intended for other objects to be accessed and
used during interaction is called an object’s interface.
A class is a template for an object and
describes what methods and properties an object of this type will have. In this
example, the class represents a person. For each person in your application,
you can make a separate instance of this class that represents the person’s
information. For example, if two people in our application are called Joe and
Judy, we would create two separate instances of this class and would call the
setName() method of each with their names to initialize the variable holding
the person’s name, $name. The methods and members that other interacting
objects may use are a class’s contract. In this example, the person’s contracts
to the outside world are the two set and get methods, setName() and get-
Name().
class Person
Methods:
setName($name)
getName()
Properties:
$name
Fig. 3.1 Diagram of class Person.
The following PHP code defines the class, creates two instances of it, sets
the name of each instance appropriately, and prints the names:
class Person {
private $name;
function setName($name)
{
$this->name = $name;
}
function getName()
{
return $this->name;
}
};
$judy = new Person();
$judy->setName(”Judy”);
$joe = new Person();
$joe->setName(”Joe”);
print $judy->getName() . “\n”;
print $joe->getName(). “\n”;