Attribut vide

	public function select_teacher($mail){
		require_once(MODEL . 'Professor.php');
		$query = "SELECT * FROM teacher WHERE mail LIKE '$mail'";
		$result = $this->_db->query($query);
		$teacher = null;
		if ($result->rowcount() == 0) {
			return $teacher;
		}else{
			while ($row = $result->fetch()) {
				$teacher = new Professor($mail, $row->name, $row->firstname, $row->role);
			}
		}
		return $teacher;
	}

			$teacher = Db::getInstance()->select_teacher($mail);
			var_dump($teacher);
			var_dump($teacher->get_role());
			if($teacher->get_role() == 'true'){
				$role = 'admin';
			}