php设计模式之单例模式代码

php设计模式之单例模式的例子，供大家参考，具体内容如下

    <?php
      /**
       * php设计模式 单例模式
       */
      class Fruit{
        private static $instanceMap = array();

        //protected getter for singleton instances
        protected static function getSingleton($className){
          //保证单例模式 并且不能从控制器实例化和克隆
          if (!isset(self::$instanceMap[$className])) {
            $object = new $className;
            //Make sure this object inherit from Singleton
            if ($object instanceof Fruit) {
              self::$instanceMap[$className] = $object;
              var_dump($object);
            } else {
              throw SingletonException("Class '$className' do not inherit from Singleton!");
            }
          }
          return self::$instanceMap[$className];
        }

        //protected constructor to prevent outside instantiation
        protected function __construct(){}

        //denie cloning of singleton objects
        public final function __clone(){
          trigger_error('It is impossible to clone singleton', E_USER_ERROR);
        }
      }

      class Apple extends Fruit{
        protected $rndId;

        public function __construct(){
          $this->rndId = rand();
        }

        public function whatAmI(){
          echo 'I am a Apple(' . $this->rndId . ')<br />';
        }

        public static function getInstance(){
          //echo get_class();
          return Fruit::getSingleton(get_class());
        }
      }

      class GreenApple extends Apple{
        public function whatAmI(){
          echo 'I am a GreenApple(' . $this->rndId . ')<br />';
        }

        public static function getInstance(){
          return Fruit::getSingleton(get_class());
        }
      }

      $apple1 = Apple::getInstance();
      //var_dump($apple1);
      $apple2 = GreenApple::getInstance();
      $apple1->whatAmI();// should echo 'I am a Apple(some number)
      $apple2->whatAmI();// should echo 'I am a GreenApple(some number)
      $apple1 = Apple::getInstance();
      $apple2 = GreenApple::getInstance();
      //保证单例模式
      $apple1->whatAmI();// should echo 'I am a Apple(same number as above)
      $apple2->whatAmI();// should echo 'I am a GreenApple(same number as above)
      // $a = clone $apple1;// this should fail
      // $b = clone $apple2;// this should fail

以上就是本文的全部内容，希望对大家学习php程序设计有所帮助。