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 );
}

}