為什么echo BigCar::start(); 輸出不了？
<?php
class Car {
??? private static $speed = 1100;
?? ?
??? public static function getSpeed() {
??????? return self::$speed;
??? }
?? ?
??? public static function speedUp() {
??????? return self::$speed+=120;
??? }
}
class BigCar extends Car {
??? public static function start() {
?? ?
??? parent::speedUp();
??? }
}
echo BigCar::start();
echo BigCar::getSpeed();
2017-05-05
沒(méi)寫(xiě)return。
class BigCar extends Car {
??? public static function start() {
? ????return ? parent::speedUp();
??? }
}
2017-07-25
為何兩個(gè)輸出都是1220
第二個(gè)不應(yīng)該是1100嗎？