单例模式

<?php// 单例模式class Singleton{protected static $ins = null;/** * 禁止子类重载 __construct() 构造方法 */private final function __construct() {// 禁止 new}/** * 禁止子类重载 __clone() 方法 */protected final function __clone() {// 禁止 clone}/*public static function getIns() {if(self::$ins === null){self::$ins = new self();}return self::$ins;}*//** * 后期静态绑定 */public static function getIns() {if(static::$ins === null){static::$ins = new static();}return static::$ins;}}$obj1 = Singleton::getIns();$obj2 = Singleton::getIns();var_dump($obj1 === $obj2); //true// $obj3 = clone $obj1; //不能被克隆