Object-Oriented Programming in PHP

Class & Object:

Class is a programmer-defined data type, which includes local methods and local variables. It is a collection of objects. Object has properties and behaviour.

First we have to define a php class, where classname should be same as filename.

Example for simple class:

<?php
class Books{
  public function name(){
  echo "Drupal book";
  }
  public function price(){
  echo "900 Rs/-";
  }
}
//To create php object we have to use a  new operator. Here php object is the object of the Books Class.
$obj = new Books();
$obj->name();
$obj->price();
?>

Output:

Drupal book
900 Rs/-

Creating Objects in PHP

When class is created, we can create any number of objects to that class. The object is created with the help of new keyword.

Calling Member Function

When the object is created we can access the variables and method function of the class with the help of operator ‘->, accessing the method is done to get the information of that method. Also look into how we can access object properties via variables

<?php
   class Mobile {
      /* Member variables */
      var $price;
      var $title;
      /* Member functions */
      function setPrice($par){
         $this->price = $par;
      }
      function getPrice(){
         echo $this->price ."
";
      }
      function setName($par){
         $this->title = $par;
      }
      function getName(){
         echo $this->title ."
";
      }
   }
$Samsung = new Mobile();
$Xiaomi = new Mobile();
$Iphone = new Mobile();
$Samsung->setName( "SamsungS8 );
$Iphone->setName( "Iphone7s" );
$Xiaomi->setName( "MI4" );
$Samsung->setPrice( 90000 );
$Iphone->setPrice( 65000 );
$Xiaomi->setPrice( 15000 );
Now you call another member functions to get the values set by in above example
$Samsung->getName();
$Iphone->getName();
$Xiaomi->getName();
$Samsung->getPrice();
$Iphone->getPrice();
$Xiaomi->getPrice();
?>

Output:

Samsung S8
Iphone S7
MI4
90000
65000
15000

Inheritance

When the properties and the methods of the parent class are accessed by the child class, we call the concept has inheritance. The child class can inherit the parent method and give own method implementation, this property is called overridden method. When the same method of the parent class is inherited we call as inherited method. Now let us see types of inheritance supported in Object Oriented Programming and corresponding Php inheritance examples.

Types Of Inheritance

• Single Level Inheritance
• Multilevel Inheritance

Single Level Inheritance:

In Single Level Inheritance the Parent class methods will be extended by the child class. All the methods can be inherited.

Example for Single Level Inheritance

<?php
class A {
    public function printItem($string) {
        echo 'Hi : ' . $string . "\n;
    }
    public function printPHP() {
        echo 'I am from valuebound' . PHP_EOL;
    }
}
class B extends A {
    public function printItem($string) {
        echo 'Hi: ' . $string . PHP_EOL;
    }
 public function printPHP() {
        echo "I am from ABC";
    }
}
$a = new A();
$b = new B();
$a->printItem('Raju');
$a->printPHP();       
$b->printItem('savan');
$b->printPHP();       
?>

Output:

Hi : Pavan
I am from valuebound
Hi: savan
I am from ABC

MultiLevel Inheritance :

In MultiLevel Inheritance, the parent class method will be inherited by child class and again subclass will inherit the child class method.

<?php
class A {
	public function myage() {
	return  "age is 80\n";
	}
}
class B extends A {
	public function mysonage() {
	return "age is 50\n";
	}
}
class C extends B {
	public function mygrandsonage() {
	return  "age is 20\n";
	   }
        public function myHistory() {
        echo "Class A " .$this->myage();
        echo "Class B ".$this-> mysonage();
        echo "Class C " . $this->mygrandsonage();
        }
}
$obj = new C();
$obj->myHistory();
?>

Output:

Class A age is 80
Class B age is 50
Class C age is 20