php 单例模式实例

<?php 
/** 
 *single pattern 
 *@auth webtechnic@qq.com
 */
class SinglePattern{
	//保存单一实例
	private static $instance;
	//属性
	private $val;
	//getter and setter 方法
	public function setVal($val){
		$this->val = $val;
	}
	
	public function getVal(){
		return $this->val;
	}
	
	//受保护的构造方法，不允许通过new创建类实例
	private function __construct(){
		
	} 

	//唯一取得类实例的方法
	public static function getInstance(){
		if(!self::$instance){
			self::$instance = new SinglePattern();
		}
		return self::$instance;
	}
	
	//
	public function __toString(){
		return $this->val;
	}
}
//测试 
$test = SinglePattern::getInstance();
$test->setVal("23");
echo "{$test}<br>";
$test2 = SinglePattern::getInstance();
echo "{$test2}<br>";

?>