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