设计模式----单例模式

<?php class TestSingleton {     private $sinVar = NULL;     static private $testSingleton = NULL;         private function __construct() {         echo "Create Singleton Object Now!/n";     }         static public function instance() {         if (!(self::$testSingleton instanceof TestSingleton)) {             self::$testSingleton = new TestSingleton();         }         return self::$testSingleton;     }        //  private function __clone() {    //  }        public function setSinVar ($sinVar) {         $this->sinVar = $sinVar;     }         public function getSinVar() {         return $this->sinVar;     } } $a = TestSingleton::instance(); $b = TestSingleton::instance(); $a->setSinVar('zhangxk'); $b->setSinVar('zhangxk0103'); echo $a->getSinVar(); echo "<br>"; echo $b->getSinVar();