Help with php fatal uncaught error on retrieving data from db

class DB {
   
     private static $_instance = null;
     private $_pdo,
                $_query,
                $_error = false,
                $_results,
                $_count = 0;
     
        private function __construct(){
            try {
                $this->_pdo = new PDO('mysql:host=' . Config::get('mysql/host') .  '; dbname=' . Config::get('mysql/db'), Config::get('mysql/username'), Config::get('mysql/password'));
            } catch (PDOException $e) {
                    die($e->getMessage());
            }
        }
       
        public static function getInstance(){
            if(!isset(self::$_instance)){
                self::$_instance  =  new DB();
            }
            return self::$_instance;
        }
       
        public function query($sql, $params = array()){
            $this->_error = false;

           
if (empty($params)) {
if($this->_query->query($sql)) {
                    $this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
                    $this->_count = $this->_query->rowCount();
                }

 else{
                    $this->_error = true;
                }
} else if(!empty($params)) {
            if($this->_query = $this->_pdo->prepare($sql)) {
                $x = 1;
               
                if(count($params)) {
                    foreach ($params as $param) {
                        $this->_query->bindValue($x, $param);
                        $x++;
                    }
                }
               
                if($this->_query->execute()) {
                    $this->_results = $this->_query->fetchAll(PDO::FETCH_OBJ);
                    $this->_count = $this->_query->rowCount();
                }
                else{
                    $this->_error = true;
                }
            }
            }
            return $this;
        }
       
        public function action($action, $table, $where = array()) {
            if(count($where) ===3) {
                $operators = array('=',  '>',  '<',  '>=', '<=');
               
                $field = $where[0];
                $operator = $where[1];
                $value = $where[2];
               
                if (in_array($operator, $operators)){
                    $sql = "{$action} FROM {$table} WHERE {$field} {$operator} ?";
                   
                    if(!$this->query($sql, array($value))->error()){
                        return $this;
                    }
                   
                }   
                   
            }
else if (empty($where)) {
    $sql = "{$action} FROM {$table}";

     if(!$this->query($sql, array())->error()){
                        return $this;
                    }

}
            return false;
        }
       
         public function get($table, $where) {
             return $this->action('SELECT *', $table, $where);
        }
       
        public function insert($table, $fields = array()) {
             if(count($fields)){
                 $keys = array_keys($fields);
                 $values = ' ';
                 $x =1;
                 
                 foreach ($fields as $field){
                     $values .= '?';
                     if($x < count($fields)){
                         $values .= ', ';
                     }
                     $x++;  
                 }
                 
                 $sql = "INSERT INTO {$table} (`" . implode('`, `', $keys) . "`) VALUES ({$values})";
                 
                 if(!$this->query($sql, $fields)->error()) {
                     return true;
                 }
             }
             return false;
        }
       
          public function results() {
            return $this->_results;
        }
       
         public function first() {
            return $this->results()[0];
        }
       
        public function error() {
            return $this->_error;
        }
       
         public function count() {
            return $this->_count;
        }
       
       
       
}

$user = new User();
try {
    $userd = $user->getmore('users', array());
} catch (Exception $e) {
                 die($e->getMessage());
             }   
             
        $useru =$userd->getallr();
       
foreach($useru as $user) {
echo $user['email'];
}

class User{
   
    private $_db,
                $_sessionName,
                $_cookieName;
        public $udatas = array();

    public function __construct($user = null) {
        $this->_db = DB::getInstance();
        $this->_sessionName  =  Config::get('session/session_name');
        $this->_cookieName  =  Config::get('remember/cookie_name');
      }

            public function create ($tabla, $fields = array()) {
        if(!$this->_db->insert("$tabla", $fields)) {
            throw new Exception("There was a problem creating");
        }
       
    }
   
    public function getmore($table, $input) {
         if(!$this->_db->get("$table", $input)) {
            throw new Exception("There was a problem gettibg");
        }
    }
   
    public function getallr() {
        $this->udatas = $this->_db->results();
        return $this->udatas;
    }

}