5 回答class Truck extends Car{ public function speedUp(){ $this->speed=parent::speedUp()+50; } }

1 回答子類Truck中$this->speed是指向父類Car中的變量嗎

3 回答$car = new Car(); 什么意思

2 回答$car->speed,為什么不是$car->$speed?

4 回答<?php class Car { private function __construct(){ echo 'object creat'; } private static $_object = null; public static function getInstance(){ if(empty(self::$_object)){ self::$object = new Car(); }