php电子书

				4-7-1.php				instanceof运算符.								class User{					private $name;					public function  getName(){						return "UserName is ".$this->name;					}				}								class NormalUser extends User {					private $age = 99;					public function getAge(){						return "age is ".$this->age;					}				}								class UserAdmin{ //操作.					public static function  getUserInfo(User $_user){						echo $_user->getAge();					}				}				$normalUser = new NormalUser();				UserAdmin::getUserInfo($normalUser);				?>