ZEND PHP 5 Certification STUDY GUIDE

114 ” Object Oriented Programming in PHP
just blueprints that cannot be used directly—they must be instantiated into objects,
which can then interact with the rest of the application. You can think of classes as
the blueprints for building a car, while objects are, in fact, the cars themselves as
they come out of the production line. Just like a single set of blueprints can be used
to produce an arbitrary number of cars, an individual class can normally be instantiated
into an arbitrary number of objects.
Declaring a Class
The basic declaration of a class is very simple:
class myClass {
}
// Class contents go here
As you have probably guessed, this advises the PHP interpreter that you are declaring
a class called myClass whose contents will normally be a combination of constants,
variables and functions (called methods).
Instantiating an Object
Once you have declared a class, you need to instantiate it in order to take advantage
of the functionality it offers. This is done by using the new construct:
$myClassInstance = new myClass();
In PHP 5, objects are treated differently from other types of variables. An object is
always passed by reference (in reality, it is passed by handle, but for all practical
purposes there is no difference), rather than by value. For example:
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$myClassInstance = new myClass();
$copyInstance = $myClassInstance();