Pdo autocompletion

Hi,
I am setting op a db class as an excercise to learn php a bit better.
In the code below in the method querydb I get a warning from phpstorm that it does not now
about the $this->dblink and also the method $this-dblink->query is unknown.
What am I doing wrong ?

class dbclass
{
    var $dbhost;
    var $dbname;
    var $dbuser;
    var $dbpass;
    var $dbschema;
    var $dblink;

    function __construct($h, $n, $u, $p, $s)
    {
        $this->dbhost = $h;
        $this->dbname = $n;
        $this->dbuser = $u;
        $this->dbpass = $p;
        $this->dbschema = $s;
    }


    function opendb()
    {
        try {
            /*** setup the connection ***/
            $this->dblink = new PDO('pgsql:dbname=' . $this->dbname . ';host=' . $this->dbhost, $this->dbuser, $this->dbpass);
            /*** set the error reporting attribute ***/
            $this->dblink->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            /*** test the new connection ***/
            $sql = 'SELECT version()';
            $resultset = $this->dblink->query($sql);
            if ($resultset->rowCount() <= 0) {
                throw new Exception('<p>Unable to perform test query</p>');
            }
        } catch (PDOException $e) {
            echo $e->getMessage();
        } catch (Exception $e) {
            echo $e->getMessage();
        }

    }

    function querydb($sql)
    {
        try {
            return $this->dblink->query($sql);
        } catch (PDOException $e) {
            echo $e->getMessage();
        }
    }