Beginners Guide to Object Orientation In PHP by Rick Ogden for PHPNW09

What is Object Orientation? Object-Oriented Programming is a programming methodology that consists of multiple interacting objects, each completely self-sufficient. This allows for flexible, expandable programming Encapsulated code Protection of data Many more things beyond the scope of this tutorial

This allows for flexible, expandable programming

Encapsulated code

Protection of data

Many more things beyond the scope of this tutorial

Class A class is a blueprint of an object, and is the basis of what the object will consist of. It contains two major entities: Properties Methods A class is self sufficient by nature, and therefore can be implemented into multiple applications without modification.

Properties

Methods

A class is self sufficient by nature, and therefore can be implemented into multiple applications without modification.

Example of a Class Here we're going to create a new class for containing someone's profile information on a social networking website.

Object An object is created by creating a new instance of a class. Objects of the same class have exactly the same functionality, but the properties within the object are what makes them different. Eg. A news article on a website may be an object from a NewsArticle class, but the contents of the article will differ from another news article

Referencing In order for an object to be useful, you need to be able to call its contents. For this, PHP uses the arrow operator ( -> ). $object->property; $object->method();

$object->property;

$object->method();

Self Referencing Throughout the instance of an object, chances are it will need to reference itself (to get its properties, or call its own methods). In order for an object to reference itself, the variable $this is used in the class. $this->property; $this->method();

$this->property;

$this->method();

Properties Properties are class-wide variables. They are often initialised when an object of the class is created (although they do not have to be) They are defined at the top of the class Methods can alter and interact with these properties throughout the existence of the object

Properties are class-wide variables.

They are often initialised when an object of the class is created (although they do not have to be)

They are defined at the top of the class

Methods can alter and interact with these properties throughout the existence of the object

Adding Properties We will add some properties to our Profile class. Of course the properties are not limited to the ones here:

Methods A method is a piece of code within a class which performs a task or calculation. These are similar to functions. It can: Interact and modify properties of the object Take arguments on execution Return a value after execution None of these are compulsory (although if it doesn't do any of these, it's a bit useless!)

Interact and modify properties of the object

Take arguments on execution

Return a value after execution

None of these are compulsory (although if it doesn't do any of these, it's a bit useless!)

Method Uses Methods are used for a number of different things. These include: Retrieve data from a property in a “read only” fashion Format data Alter properties in a controlled way

Retrieve data from a property in a “read only” fashion

Format data

Alter properties in a controlled way

Method: Parameters A method can include parameters (exactly like functions) Parameters can either be required, or have a default value

A method can include parameters (exactly like functions)

Parameters can either be required, or have a default value

Constructor The constructor is called when the object is initialised. A constructor often takes parameters to initialise some (if not all) of the properties of that object It is identified in a class as it has the method name __construct (for backwards-compatibility, a method with the same name as the class also works)

A constructor often takes parameters to initialise some (if not all) of the properties of that object

It is identified in a class as it has the method name __construct (for backwards-compatibility, a method with the same name as the class also works)

Our class so far I've added a constructor to initialise the properties Added a method to return the full name of the person whose profile it is.

I've added a constructor to initialise the properties

Added a method to return the full name of the person whose profile it is.

Instantiate an Object To create an object from a class you use the “new” keyword. $object = new MyClass(); This creates a new object and calls the constructor Any arguments that need to be given to the instructor are given on creation. We will store our class in Profile.php

To create an object from a class you use the “new” keyword.

$object = new MyClass();

This creates a new object and calls the constructor

Any arguments that need to be given to the instructor are given on creation.

We will store our class in Profile.php

Why Use Encapsulation Encapsulation gives the ability to hide data from outside of the object. Gives the programmer control over what is inputted into properties (validation etc..) What form data is when it is returned from the class Ability to alter code within the class, without having to worry about needing to change code in other parts of the application

Gives the programmer control over what is inputted into properties (validation etc..)

What form data is when it is returned from the class

Ability to alter code within the class, without having to worry about needing to change code in other parts of the application

Public/Private/Protected Properties and methods can take one of 3 forms to encapsulate Public: Property/method can be accessed from anywhere, inside or outside the object Protected: Can only be accessed from within the class, or inherited class Private: Can only be accessed from directly within the class (and not subclasses)

Public: Property/method can be accessed from anywhere, inside or outside the object

Protected: Can only be accessed from within the class, or inherited class

Private: Can only be accessed from directly within the class (and not subclasses)

Inheritance Inheritance allows a programmer to reuse a class and expand it for a different purpose. Reasons: Add code to a class to make it more specialised Override existing code Why reinvent the wheel?

Add code to a class to make it more specialised

Override existing code

Why reinvent the wheel?

Cons of Object Orientation Object Orientation does not come without its drawbacks Main reason is it is less efficient than procedural code

Object Orientation does not come without its drawbacks

Main reason is it is less efficient than procedural code

Thank You Any Questions? For these slides and other things please visit my brand new website: http://www.rickogden.com/