PHP函数

<?php
echo strncmp("I love China!","I love Shanghai!",6);
?>

<?
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 $_user){
if($_user instanceof NormalUser ){
echo $_user->getAge();
}else{
echo "类型不对,不能使用这个方法.";
}
}
}
$User = new User(); // 这里new的是User.
UserAdmin::getUserInfo($User);
?>