1 <?php
2 interface USB{
3 
4     public function run();
5 }

 1 <?php
 2 include_once("./usb.interface.php");
 3 class store implements USB{
 4     
 5     public function run(){
 6         $this -> initialize();
 7     }
 8 
 9     private function initialize(){
10         echo "store running ..";
11     }
12 }

 1 <?php
 2 include_once("./usb.interface.php");
 3 class mouse implements USB{
 4 
 5     public function run(){
 6         $this -> init();
 7     }
 8 
 9     public function init(){
10         echo "mouse running ...";
11     }
12 }

<?php
include_once("./usb.interface.php");
class key implements USB{
    
    public function run(){
        $this -> init();
    }

    public function init(){
        echo "key running ..";
    }
}

<?php
include("./mouse.class.php");
include("./store.class.php");
include("./key.class.php");

class computer{

    public function useUSB($obj){
        $obj -> run();
    }
}

$computer = new computer();

$computer -> useUSB(new mouse()); 
echo "<hr />";
$computer -> useUSB(new store());
echo "<hr />";
$computer -> useUSB(new key());