prepare, execute возвращают пустые значения

В этом методе prepare, execute возвращают пустое значение

public function queryUpdateEx($queryString, $params){
    try{
        $tt = getdate();
        $query = $this->db->prepare($queryString);
        //$query->execute((array)$params);
        $qu = $query->execute($params);
        Loger::getInstance()->logUp("query \n". $params[':discription'] . "\n\n");
        if($qu){
            Loger::getInstance()->logUp("UPDATE \n".
                                        "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                        json_encode($_SERVER["HTTP_REFERER"])."\n".
                                        json_encode($params)."\n\n");
            return true;
        }
        Loger::getInstance()->logUp("NOT UPDATE \n".
                                    "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                    json_encode($_SERVER["HTTP_REFERER"])."\n".
                                    json_encode($params)."\n\n");
        return false;
    } catch(Exception $e){
        Loger::getInstance()->logUp("UPDATE ERROR \n".$e->getMessage()."\n".json_encode($params)."\n\n");
        return $e->getMessage();
    }
}

вот полностью класс

<?php
class Model
{
    protected $db;
//protected $fdb;
function __construct(){
    $this->db = new Database();
    //$this->fdb = new Databasefirebird();
}
// метод выборки данных
public function get_data()
{
}
public function queryEx($queryString, $params){
    try{
        $query = $this->db->prepare($queryString);
        $query->execute((array)$params);
        $query->setFetchMode(PDO::FETCH_ASSOC);
        $query = $query->fetchAll();
        if($query == NULL){
            Loger::getInstance()->log("WARNING empty result \n".$_SERVER["HTTP_REFERER"]."->".$_SERVER['REQUEST_URI']."\n".
                                      json_encode($params)."\n\n");
        }
        return $query;
    } catch(Exception $e){
        Loger::getInstance()->log("QUERY ERROR \n".$e->getMessage()."\n".json_encode($params)."\n\n");
        return null;   //$e->getMessage();
    }
}
public function queryInsertEx($queryString, $params){
    try{
        $tt = getdate();
        $query = $this->db->prepare($queryString);
        $qu = $query->execute((array)$params);
        if($qu){
            Loger::getInstance()->logUp("INSERT \n".
                                        "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                        json_encode($_SERVER["HTTP_REFERER"])."\n".
                                        json_encode($params)."\n\n");
            return true;
        }
        Loger::getInstance()->logUp("NOT INSERT \n".
                                    "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                    json_encode($_SERVER["HTTP_REFERER"])."\n".
                                    json_encode($params)."\n\n");

        //Loger::getInstance()->logUp(json_encode($query));
            return false;
    } catch(Exception $e){
        Loger::getInstance()->logUp("INSERT ERROR \n".$e->getMessage()."\n".json_encode($params)."\n\n");
        return $e->getMessage();
    }
}
public function queryUpdateEx($queryString, $params){
    try{
        $tt = getdate();
        $query = $this->db->prepare($queryString);
        //$query->execute((array)$params);
        $qu = $query->execute($params);
        Loger::getInstance()->logUp("query \n". $params[':discription'] . "\n\n");
        if($qu){
            Loger::getInstance()->logUp("UPDATE \n".
                                        "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                        json_encode($_SERVER["HTTP_REFERER"])."\n".
                                        json_encode($params)."\n\n");
            return true;
        }
        Loger::getInstance()->logUp("NOT UPDATE \n".
                                    "user:".$_SESSION['id']." IP:".$_SERVER['REMOTE_ADDR']." TIME:".(3+$tt['hours']."-".$tt['minutes']."-".$tt['seconds']).
                                    json_encode($_SERVER["HTTP_REFERER"])."\n".
                                    json_encode($params)."\n\n");
        return false;
    } catch(Exception $e){
        Loger::getInstance()->logUp("UPDATE ERROR \n".$e->getMessage()."\n".json_encode($params)."\n\n");
        return $e->getMessage();
    }
}
public function month($number){
    switch($number){
        case '1':
            return 'Январь';
            break;
        case '2':
            return 'Февраль';
            break;
        case '3':
            return 'Март';
            break;
        case '4':
            return 'Апрель';
            break;
        case '5':
            return 'Май';
            break;
        case '6':
            return 'Июнь';
            break;
        case '7':
            return 'Июль';
            break;
        case '8':
            return 'Август';
            break;
        case '9':
            return 'Сентябрь';
            break;
        case '10':
            return 'Октябрь';
            break;
        case '11':
            return 'Ноябрь';
            break;
        case '12':
            return 'Декабрь';
            break;
    }
}
}