<?php

interface usb1{

function type();

function add();

}

class kington implements usb1{

function type(){

echo"usb type is2.0,";

   }

function add(){

echo"add thekington...<br> ";

   }

}

class iphone implements usb1{

function type(){

echo'usb type is3.0,';

   }

function add(){

echo'add theiphone...<br>';

   }

}

class mypc{

function pcusb($what){

$what->type();

$what->add();

   }

}

$pc= new mypc();

$kingston=new kington();

$iphone=new iphone();

$pc->pcusb($iphone);

$pc->pcusb($kingston);

class A{}

class B{}

$a=new A();

$b=new B();

if($ainstanceof A){

echo'A';

}

if($binstanceof B){

echo'B';

}

http://localhost/php/24.php

usb type is 3.0,add the iphone...
usb type is 2.0,add the kington...
AB