Class & Object in Php

Introduction

• Class and Object are one of the most important features of OOPs.

Definition

Class

• • A class is simply a template for objects.
  • A class is created by using the ‘class’ keyword, followed by the name of the class and a pair of curly braces ({}). All the properties/variables and methods/functions are written inside these braces.
  • A class may be one or more objects as per need.
  • Syntax:
    • <?php
      class ClassName {
        // single or multiple source codes statements;
      }
      ?>
  • Example:
    • <?php
      class Msg {
        echo “Hello India”;
      }
      ?>
    • Click this link for full Example details.

Object

• • An object is an instance of a class.
  • At least one object is necessary for a class i.e., there is no meaning of a class without an object.
  • Objects are created using the ‘new’ keyword.
  • When an individual object is created for a class then the created object inherits all the properties and behaviors templates of the class, but each object has its own (different) values of the properties.
  • The properties and methods of a class are called using object name -> (operator) and then properties or methods name. 
  • Syntax:
    • <?php
      class ClassName {
        // single or multiple source codes statements;
      } 

   $ObjectName=new ClassName();

• • Example:
    • Click this link for full Example details.

‘this’ keyword

• • The ‘this’ keyword in Php is used to represent the current object.
  • ‘this’ keyword is only applicable inside methods of a class.
  • Example:
    • Click this link for full Example details.

‘instanceof’ keyword

• •  The ‘instanceof’ keyword is used to check that an object belongs to a specific class.
  • Example:
    • Click this link for full Example details.

Access Specifier or Modifiers in Php

• Access Specifier is a way to control the object to access the properties and methods of a class.
• There are three access modifiers in Php:-
  • Public : 
    • In this access specifier, the property or method can be accessed directly by an object of the same or different class.
    • This specifier has no security.
    • This is the default access specifier in Php.
  • Protected :
    • In this access specifier, the property or method can be accessed by an object of the same class or derived class.
  • Private :
    • In this access specifier, the property or method can only be accessed by an object of the same class.
    • This specifier has the highest security.