# INTRODUCTION on Object Oriented

# Object-Oriented

PHP Object Oriented Concepts :

Before we go in detail, lets define important terms related to Object Oriented Programming :

- Class:This is a programmer-defined data type, which includes local functions as well as local data. You can think of a class as a template for making many instances of the same kind (or class) of object.
- Object:An individual instance of the data structure defined by a class. You define a class once and then make many objects that belong to it. Objects are also known as instance.
- Member Variable:These are the variables defined inside a class. This data will be invisible to the outside of the class and can be accessed via member functions. These variables are called attribute of the object once an object is created.
- Member function:These are the function defined inside a class and are used to access object data.
- Inheritance:When a class is defined by inheriting existing function of a parent class then it is called inheritance. Here child class will inherit all or few member functions and variables of a parent class.
- Parent class:A class that is inherited from by another class. This is also called a base class or super class.
- Child Class:A class that inherits from another class. This is also called a subclass or derived class.
- Polymorphism:This is an object oriented concept where same function can be used for different purposes. For example function name will remain same but it make take different number of arguments and can do different task.
- Overloading:a type of polymorphism in which some or all of operators have different implementations depending on the types of their arguments. Similarly functions can also be overloaded with different implementation.
- Data Abstraction:Any representation of data in which the implementation details are hidden (abstracted).
- Encapsulation:refers to a concept where we encapsulate all the data and member functions together to form an object.
- Constructor:refers to a special type of function which will be called automatically whenever there is an object formation from a class.
- Destructors:refers to a special type of function which will be called automatically whenever an object is deleted or goes out of scope.

### Example 1 (Accessing Member Variable) :

<?php

class room

{

var $str=”hello”; //member variable

}

$obj=new room();

echo $obj->str; //accessing member variable

?>

output:

hello

### Example 2 (Accessing Member Function) :

<?php
class room
{

var $length; //member variable
var $width; //member variable
var $area; //member variable

function area($a,$b) //member function
{
$this->length=$a;
$this->width=$b;
$this->area=$this->length*$this->width;
echo “area is =”.$this->area;
}
}
$obj=new room();
$obj->area(10,20); //accessing member function

?>

ouput:
area is 200

###

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