What’s the point of interfaces in PHP?

We have three different classes as follows:

class Circle {public function draw() {//} public function setRadius() {//}} class Square {public function draw() { //}} class Rectangle {public function draw() {//}} 

Now, as shown above, we have the same function in all three draw()classes and another function in the Circle class as setRadius() . We now have three different interfaces created and implemented in our classes as follows:

interface Shape {public function draw(); } interface Radius {public function setRadius(); } interface Main {public function process(); } class Circle implements Shape, Radius, Main {public function draw() {echo "Drawing Circle ..."; } public function setRadius() {echo "Setting Radius ..."; } public function process() {$this-> setRadius(); $this-> draw(); }} class Square implements Shape, Main {public function draw() {echo "Drawing Square ..."; } public function process() {$this-> draw(); }} class Rectangle implements Shape, Main {public function draw() {echo "Drawing Rectangle ..."; } public function process() {$this-> draw(); }} 

As shown above, we have implemented more than one interface in our classes. The Shapeand Maininterfaces are implemented in all classes, and the Radiusinterface is implemented only in the Circle class.Then there is the fourth class named DrawShape, soas we want to call the process()function in all classes. The process()function should call all functions in this class.

class DrawShape {public function newShape (Main $shape) {return $shape-> process(); }} 

Example : interface Shape { public function draw(); } interface Radius { public function setRadius(); } interface Main { public function process(); } class Circle implements Shape, Radius, Main { public function draw() { echo "Drawing Circle ..." ; echo "
" ; } public function setRadius() { echo "Setting Radius ..." ; } // To call all functions in this class public function process() { $this -> setRadius(); $this -> draw(); }  
} class Square implements Shape, Main { public function draw() { echo " Drawing Square ... " ; echo "
" ; } // To call all functions in this class public function process() { $this -> draw(); }  
} class Rectangle implements Shape, Main { public function draw() { echo " Drawing Rectangle ... " ; echo "
" ; } // To call all functions in this class public function process() { $this -> draw(); }  
} class DrawShape {   public function newShape (Main $shape ) { return $shape -> process(); }  
}  
// Draw a circle $shapeCircle = new Circle(); $drawCircle = new DrawShape(); $drawCircle -> newShape ( $shapeCircle );  
// Draw a square $shapeSquare = new Square(); $drawSquare = new DrawShape(); $drawSquare -> newShape ( $shapeSquare );  
// Draw rectangle-method/">rectangle $shapeRectangle = new Rectangle(); $drawSquare = new DrawShape(); $drawSquare -> newShape ( $shapeRectangle );  
?> Output: