关于单例模式的问题~

<?php/** * Created by PhpStorm. * User: Administrator * Date: 2015/8/30 * Time: 12:53 */class Singleton{    private static $instance = null;    private function __construct($name){        $this->name = $name;    }    public static function getInstance(){        if(self::$instance==null){            return new Singleton("");        }        return self::$instance;    }    public function printString(){        echo "hello,this is printString()"."<br/>";    }    public function setName($name){        $this->name = $name;    }    public function getName(){        echo "The name is ".$this->name."<br/>";    }}$class = Singleton::getInstance();$class->printString();$class->setName("jack");$class->getName();$class2 = Singleton::getInstance();$class2->getName();

<?php/** * Created by PhpStorm. * User: Administrator * Date: 2015/8/30 * Time: 12:53 */class Singleton{    private static $instance = null;    private function __construct($name){        $this->name = $name;    }    public static function getInstance(){        if(self::$instance==null){            return new Singleton("");        }        return self::$instance;    }    public function printString(){        echo "hello,this is printString()"."<br/>";    }    public function setName($name){        $this->name = $name;    }    public function getName(){        echo "The name is ".$this->name."<br/>";    }}$class = Singleton::getInstance();$class->printString();$class->setName("jack");$class->getName();$class2 = Singleton::getInstance();$class2->getName();