使用PEAR连接到数据库时出错

我想用PEAR开发一个网站，我已经创建了一个类来连接和断开与数据库的连接，但它似乎不起作用。我问你，关于下面的代码，我哪里错了？

class DB {
    private $mdb2;
    private $connected ;
    private $error;
    public function __construct(){
        $this->mdb2 = $mdb2;
        $this->connected = false;
        $this->error = "";
    }

    public function Connect(){
        require_once('config.php');
        $this->mdb2 = MDB2::connect("mysql://".$db_user.":".$db_pass."@".$db_host."/".$db_name."");
        $this->connected = true;
        if (PEAR::isError($this->mdb2))
        {
            //error handling
            $this->connected = false;
            die("Error connecting to the database!".$this->mdb2->getMessage());
        }
        return $this->connected;
    }
    public function getError(){
        return $this->error;
    }
    public function doquery($query)
    {
        if ($query != "" && $this->connected == true)
        {
            $result = $this->mdb2->query($query);
            if ($result->numRows() > 0 )
            {
                return $result;
            }
            else 
            {
                $this->error = "The Query returned 0 rows";
            }
        }
        else 
        {
            $this->error = "Invalid Query or DB Connection Closed";
        }
    }
    public function Disconnect(){
        if ($this->connected == true)
        {
            $this->connected = false;
            $this->mdb2->disconnect();
        }
        else 
        {
            $this->connected = false;
        }
    }
 }

运行此代码进行测试：

 $cdb = new DB();
 $cdb->Connect();
 $data = $cdb->doquery("SELECT test FROM test");
 $aa = 0;
if ($cdb->getError() == ""){
while ( $line = $data->fetchRow())
   $aa = $line[0];
   echo $aa;
}
 else echo $cdb->getError();
 $cdb->Disconnect();
 if ($aa == 3){
 $cdb->Connect();
 $dataa = $cdb->doquery("SELECT test FROM test");
 while ( $linea = $dataa->fetchRow())
   echo $linea[0];
 $cdb->Disconnect();
 }

给我这个错误：

MDB2错误：连接失败连接：[错误消息：用户'test'@'localhost'（使用密码：NO）访问被拒绝][本机代码：1045][本机消息：用户'stest'@'localhost'访问被拒绝[使用密码：NO）]**mysql（mysql）：//：xxx@/