conn = mysql_connect('localhost','root','');}//创建一个用来实例化对象的方法public static function getinstance(){if(!(self::$conn instanceof self)){self::$conn = new self;}return self::$conn;}//防止对象被复制public function __clone(){trigger_error('clone is not allowed !');}}
//只能这样取得实例，不能new 和 clone$mysql = mysql::getinstance();?>
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