Abstrakte PHP-Klasse

abstract class FlyIdea {    // 大力引擎
    public abstract function engine();    // 平衡舵
    public abstract function balance();

    /*
         注意：抽象方法中 不能有方法体
         下面这样写是错误的         public abstract function balance() {

         }
         报错如下：
         Fatal error: Abstract function FlyIdea::balance() cannot contain body
    */
}

/*
抽象类不能new 来实例化
$kongke = new FlyIdea();

报错如下：
Fatal error: Cannot instantiate abstract class FlyIdea
*/

abstract class Rocket extends FlyIdea {

    public function engine() {
        echo &#39;点燃火药，失去平衡。<br >&#39;;
    }
}class Fly extends Rocket {
    public function engine() {
        echo &#39;用力一扔<br >&#39;;
    }    public function balance() {
        echo &#39;两个纸翼保持平衡~~~~~~&#39;;
    }    public function start() {
        $this->engine();        for($i=0;$i<10;$i++) {            $this->balance();            echo &#39;平稳飞行<br >&#39;;
        }
    }
}$apache = new Fly();$apache->start();

abstract class Welcome {
    public abstract function wel();}class china extends Welcome {
    public function wel() {
        echo &#39;你好，非死不可<br >&#39;;
    }
}class english extends Welcome {
    public function wel() {
        echo &#39;hi,welcome<br >&#39;;
    }
}class japan extends Welcome {
    public function wel() {
        echo &#39;搜达斯奈<br >&#39;;
    }
}$c = &#39;china&#39;; //english //japan$wel = new $c();$wel->wel();