class rect
{
   public $length=0;

   public $width=0;

   public $area=0;

   public function getData()

   {

      $this->length=10;

      $this->width=20;

   }

   public function area()

   {

      $this->area = $this->length * $this->width;

   }

   public function showArea()

   {

      echo "Area of $this->length and $this->width is $this->area";

   }

}

    $rect = new rect();

    $rect->getData();

    $rect->area();

    $rect->showArea();

?>

What is a class?
A class represents an object, with associated methods and variables.
Class is nothing without creating an object.To create a class we use keyword 'class'. Class Definition is Similar to defining a function......The definition does not do anything by itself. It is a blueprint, or description, of an object. To do something, We need to use the class.

An example class definition for a rect:-
The rect object has three attributes, length, width and area and can perform the action of area.
Use of $this in a class:- The $this is a built-in variable (built into all objects) which points to the current object. Or in other words, $this is a special self-referencing variable. we use $this to access properties and to call other methods of the current class.

Instantiate/create your object:-
Classes are the blueprints/templates of php objects. Classes don't actually become objects until you do something called: instantiation.

The 'new' keyword:-
To create an object out of a class, you need to use the 'new' keyword.

Steps:-

 class rect {           // Define the name of the class.

 public $length; public $width; public $area;  // Define an object of attribute (variables) the length and width of a rectangle.

public function getData(), public function area() and public function showArea() are object actions (functions).