public function getTermSignal()
    {
        $this->requireProcessIsTerminated(__FUNCTION__);

        if ($this->isSigchildEnabled() && -1 === $this->processInformation['termsig']) {
            throw new RuntimeException('This PHP has been compiled with --enable-sigchild. Term signal can not be retrieved.');
        }

        return $this->processInformation['termsig'];
    }