PHP OOP接口类型继承

像这样的代码:

interface entite
{
}
class Foo implements entite
{
}

$foo = new foo;
if( $foo instanceof entite ) echo "he is";

显示"he is"。Foo从接口继承"entite"类型但是当你尝试:

class FooDeleter implements deleter
{
public function __construct(Foo $Foo)
{
}
}
interface deleter
{
public function __construct(entite $entite);
}

给我:

Fatal error: Declaration of FooDeleter::__construct() must be compatible with deleter::__construct(entite $entite)

为什么?怎么做?= (

编辑:唯一的方法实际上是像这样定义类型化删除器:

class FooDeleter implements deleter
{
public function __construct(entite $Foo)
{
    if( $Foo instanceof Foo ) { ... }       
}
}