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In this tutorial we will cover the following:

• What is an exception?
• The use of a try…catch block
• Anatomy of PHP5 Exception class
• Extending the Exception class
• A note on unhanded exceptions

In this PHP tutorial we will understand the following:

• Meaning of Final Class
• Meaning of Final Method
• When to declare a class as final
• When to declare a method as final

In this tutorial you will learn all about static data members and methods

• Meaning of static data members
• Meaning of static methods
• Defining static data members in PHP5
• Defining static methods in PHP5
• Accessing static data members in PHP5
• Accessing static methods in PHP5
• Rules to keep in mind for static methods

In the tutorial we will understand what is Inheritance in general and how to inherit classes in PHP5.

Definition of Inheritance:

Inheritance is the mechanism of deriving a new class from an existing class. It allows a sub-class / child class to share/inherit the attributes and behaviors of a base-class or parent class. These inherited attributes and behaviors are usually modified by means of extension.

In PHP4 the only constants that we would declare were global constants. In PHP5 it is possible to define a class level constant. These constants are specific to the class and hence don’t clutter the global level constant space.

PHP5 introduces a new operator by the name of instanceOf. instanceOf is used to check if two objects passed as operands belong to the same class. This check can also happen when an object is compared with a class name.

In PHP4 a similar functionality existed with a method is_a(), which has been replaced by the instanceOf operator in PHP5.

$this variable is a pointer to the object making the function call. $this variable is not avialable in static methods. We will learn more about static methods in the next series of tutorials.

Refer to the code below which is a PHP5 Stack Class - an implementation of Stacks. You are free to use it in your programs.

PHP5 Introduces Method Type Hinting. Type Hinting allows a function to force parameters to be objects of a particular class by specifying the name of the class in the function prototype.

Type Hinting is optional in all cases except catch block.

In the earlier tutorials we have witnessed keywords like public, private and protected. These are nothing but access specifiers. So, lets understand what access specifiers are.

Definition of Access Specifiers
Access specifiers specify the level of access that the outside world (i.e. other class objects, external functions and global level code) have on the class methods and class data members. Access specifiers can either be public, private or protected.