How to show boolean false whenever the query is false with PDO [duplicate]

function run($values = array()){
    switch($this->query_type){
        case 'select':
           // return $this->query;
           echo 1;
            $stm = self::$con->prepare($this->query);
            echo 2;
            if($stm){
                echo 5;
                if($stm->execute($values)) {
                    
                    echo 4;
                    $data = $stm->fetchAll(PDO::FETCH_ASSOC);
                    if (is_array($data) && count($data) > 0) {
                        return $data;
                    }
                }else{
                    echo 6;
                }
           
            }
            break;
           
        case 'insert':
            self::$con->query($this->query);
            return true;
        case 'update':
            $stm = self::$con->prepare($this->query);
            $stm->execute($values);
            return false;
        case 'delete':
            $stm = self::$con->prepare($this->query);
            $stm->execute($values);
            return false;
        default:
            return false;

    }
    return false;
}`

How can i get false whenever that query fails i.e when some one who is not i db is trying to login?