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。