PHP Object Oriented Programming (OOP) | Introduction to object oriented programming in PHP

Object Oriented Programming in PHP

Introduction : 

• Like C++ and java, PHP also supports Object Oriented Programming (OOP) concepts.
• OOP was introduced in PHP3 and improved further. OOP supports cleaner designs, easier maintenance and greater code reuse. It also speeds up the development of large applications.
• It include the fundamental connection between data and code that works on that data.
• The class and object are fundamental construct behind object oriented Programming.
• Objects can represent real world entity like student, employee or it can represent conceptual entity like bank account, file etc.
• Objects with similar characteristics are grouped together into a single unit called class.

Advantages of Object-Oriented Programming :

• Modularization : The application can be divided into modules.
• Re-usability :  An application can be implemented by adding new modules to the existing  modules. This speed up the application development time.

 

Class :

• Class is a collection of data members (variables) and functions.
• It is programmer defined data type which include variables and functions.
• variable within class called properties and functions are called methods which represent action associated with class.
• Class is collection of objects an object has properties and behaviour.
• Class define using keyword ‘class’ followed by the name class name.
• Inside class define variables and functions

Systax :

<?php

Class class_name

{

   Properties:

    Methods

}  end of class

?>

 

Declaring properties :

• Property of a class can be defined as private, public or protected.
• Property declaration is optional.
• Using access modifier you can change the visibility of properties.
• Properties that are accessible outside the class using object should be declared as public.
• Properties that can be accessed by method within the same class should be declare private.
• Properties declared as protected can only accessed by the object class method and the class method of the classes inheriting form the class.
• If visibility is not specified it it public by default.

Example :

<?php

Class Demo

{

                Private $name =”Priya”;

                Protected $age = “19”;

                Public $class=”SYBCA”;

}

?>

Declaring Methods :

• A method is a function defined inside class.
• Using $this variable of an a object can be accessed inside the member function of a class
• Using access modifier you can change the visibility of methods.
• Methods that accessible outside the class using object is declared as public.
• Methods within same class should be declared private.
• Method that declare protected can be called from within the object class
• $this-> used to access properties of current invoking object.
• Methods and the class method of classes inheriting form the class.

Example :

<?php

Class Employee

{

                Private $emp_code;

                Private $emp_name;

                Private $emp_designation;

                Public function accept($c,$n,$d)

{

                this-> emp_code=$c;

                this-> emp_name=$n;

                this-> emp_designation=$d;

}

Function display(){

echo “EMP CODE : ”. this-> emp_code;

echo “<br>EMP NAME : ”. this-> emp_name;

echo “<br>EMP DESIGNATION : ”. this-> emp_designation;

}

}

?>

 

Objects :

 

• Object is an individual instance of class
• When define class then declare object of that class.
• Building an object using class is known as instantiation.
• Instantiating required for
• Memory allocation into which load the object
• The data that populate value of properties
• Each object contain data and code to manipulate the data.
• Object of different classes are interact with each other.

Declaring Object :

Syntax :

$object =new class;

Example :

$emp = new Employee;

Accessing properties and methods :

Methods and properties accessed using object instance using object access operator(->)

Syntax :

    $object->property_name

    $object->method_name([arg,....])

Example :

    $emp->accept(1,”Atharv”,”Manager”);

    $emp->display();

 

Initializing an object using constructor :

• A constructor allow to initialize an objects properties
• If you create a __construct() function, PHP will automatically call this function when you crate an object form a class
• It start with two underscore (_ _)

Syntax :

function __construct(args..)

{

                //definition

}

The argument that are passed to constructor that initialize the properties of the classes.

Destroying on object using destructor:

• When an object is destroyed then destructor is called it.
• It does not take any parameter.

Syntax:

Function __destruct () {

                //definition

}