mysql模块部分功能的简单封装

  class mysql
   {
       private $db;                // datebase connect
       private $result;           // mysql result
       static private $mysql;  // mysql object

       private function  __construct()
       {    // The work before Create an object
           $this->db = mysql_connect('localhost','root','');
           mysql_select_db('hello', $this->db );
       }
       public static function getObject()
       {    //if have a object,return that object,Not create
           if(! self::$mysql instanceof self)
                self::$mysql = new self;

           return self::$mysql;
       }
       public function query($sql)
       {
           $this->result = mysql_query($sql, $this->db);
           return $this->result;
       }
       public function fetch()
       {
           if( isset($this->result ) )
              return  mysql_fetch_assoc( $this->result );
       }
       public function error()
       {
           return 'error:'.mysql_error();
       }
       public function num()  // for sql select result
       {
           return mysql_num_rows( $this->result );
       }
       public function close() 
       {     // return true or false
            return mysql_close( $this->db );
       }

  }

这样做看起来就只对可移植有用，其它的作用还体会不到