PHP5.4新特性trait

php 
//代码片段1
class Hello {  
    public $id = 2;  
    public function __construct() {  
        echo 'constructHello! 
';  
    }  
    public function sayHello() {  
        echo 'Hello 
';  
    }  
}  
interface World {  
    public function sayWorld(); 
    //{  
        //echo 'World 
';  
    //}  
}  
  
class MyHelloWorld extends Hello implements World{  
    public function __construct() {  
        echo 'constructMyHelloWorld 
';  
    }  
    public function sayHello() {  
        echo 'Hello
';  
    }  
    //use Hello, World; 
    public function sayWorld(){
        echo 'World 
';
    } 
    public function saySelf() {  
        echo '!
';  
    }  
}  
  
$o = new MyHelloWorld();  
$o->sayHello();  
$o->sayWorld();  
$o->saySelf();  
echo $o->id;  

//代码片段2
php 
trait Hello {  
    public $id = 2;  
    public function __construct() {  
        echo 'constructHello! 
';  
    }  
    public function sayHello() {  
        echo 'Hello 
';  
    }  
}  
trait World {  
    public function sayWorld() {  
        echo 'World 
';  
    }  
}  
  
class MyHelloWorld{  
    public function __construct() {  
        echo 'constructMyHelloWorld 
';  
    }  
    public function sayHello() {  
        echo 'Hello
';  
    }  
    use Hello, World;  
    public function saySelf() {  
        echo '!
';  
    }  
}  
  
$o = new MyHelloWorld();  
$o->sayHello();  
$o->sayWorld();  
$o->saySelf();  
echo $o->id;