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Basic
Class & Object
• Constructor & Destructor
Access Specifiers
OOP Features
• Inheritance
• Polymorphism
• Encapsulation
Abstract Class & Interface
Use of Static
Use of Final
Exception Handling

Class :

A class is user defined data type that contains attributes or data members; and methods which work on the data members. To create a class, you need to use the keyword class followed by the name of the class.
The name of the class should be meaningful to exist within the system . The body of the class is placed between two curly brackets within which you declare class data members/variables and class methods.

    class class-name {
	class body :- Data Members & Methods;
    }
    

<?php
class Customer {
    private $first_name, $last_name;
    public function customerDetails($first_name, $last_name) {
		echo "Customer first name : $first_name 
";
		echo "Customer last name : $last_name 
";
    }
    public function printText() {
		echo "Customer text goes here";
    }
}
?>

In the above program, Customer is the name of the class and $first_name/$last_name are attributes or data members. customerDetails() and printText() are methods of a class.

Object :

An object is a living instance of a class. This means that an object is created from the definition of the class and is loaded in memory.

    $obj_name = new ClassName();
    

Note :In the above syntax style, $obj_name is a variable in PHP. 'new' is the keyword which is responsible for creating a new instance of ClassName.

<?php
class Customer {
        private $first_name, $last_name;
        public function getData($first_name, $last_name) {
                $this->first_name = $first_name;
                $this->last_name = $last_name;
        }
        public function printData() {
                echo $this->first_name . " : " . $this->last_name;
        }
}
$c1 = new Customer();
$c2 = new Customer();
?>

In the above example $c1 and $c2 are two objects of the Customer Class. Both these objects are allocated different blocks in the memory.

$this variable

$this variable is a pointer to the object making the function call. $this variable is not avialable in static methods.

<?php
class Customer {
   private $name;
   public setName($name) {
        $this->name = $name;
   }
}
$c1 = new Customer();
$c2 = new Customer();
$c1->setName("Sunil");
$c2->setName("Tanmaya");
?>

In the above example, $c1 and $c2 are two separate Customer objects. Each object has its own memory to store names.But if you see the function setName() is common.During run time, how can it make a difference as to which memory location to use to store the function values. Therefore, it uses the $this variable. As mentioned earlier, $this variable is a pointer to the object making a function call.Therefore when we execute $c1->setName("Sunil"), $this in the setName() function is a pointer or a reference to the $c1 variable.