试图在PHP PDO中获取非对象的属性

Following function I used in a login page in php. Its showing a error that

" Trying to get property of non-object in...."

function Validate($userName,$encrypted_password,$dbh)
    {
        try{
            echo ("".$userName."");
            echo ("".$encrypted_password."");
            $sql = "SELECT USERCODE,PWD FROM GUSER WHERE USERCODE = :uname AND PWD = :pwd";
            echo $sql->error;
            $query = $dbh->prepare($sql);
            $query->bindParam(':uname',$userName,PDO::PARAM_STR);
            $query->bindParam(':pwd',$encrypted_password,PDO::PARAM_STR);
            $query->execute();
            $rows = $query->fetch(PDO::FETCH_NUM);
            echo ("".$rows."");
            if($rows > 0){
                echo "Login Successfull";
                header("location: home.php");
            }
            else{
                $errmsg_arr[] = 'Username and Password are not found';
                $errflag = true;
            }
            if($errflag) {
            $_SESSION['ERRMSG_ARR'] = $errmsg_arr;
            session_write_close();
            echo "Closed";
            exit();
            }
        }                   
        catch(PDOException $e) {
            echo 'ERROR: ' . $e->getMessage();
        }
        //return $getValue;

    }

Can anyone help me out.. I am new to php.. Please help

Thanks in advance

String is not an object:

$sql = "SELECT USERCODE,PWD FROM GUSER WHERE USERCODE = :uname AND PWD = :pwd"; // STRING
echo $sql->error; // but you try to access it like it's an object

$sql is string so it doesn't have properties like error and you can't access it like $sql->error, because it's a primitive value type.

You have to delete this line:

echo $sql->error;

To handle SQL errors in PDO you have to use try-catch construct in PHP. See this answer for more information about handling errors in PDO.