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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。