code: public function start(?string $name = null, ?string $sessionId = null): string
      {
          if (!$this->isStarted()) {
              if (!is_null($name)) {
                  $this->setName($name);
              }
              @session_start($sessionId);
          };
          return $this->getId();
      }
docs: It inits the data of new session or continues the current session.
  @param string $name The optional name of session, it has higher priority
  than the $iSess parameter.
  @param string $sessionId The optional session ident. It ignored if the $sSessName
  parameter was passed.
  @return string The id of current session.