think\Process::getIncrementalErrorOutput PHP Method

    public function getIncrementalErrorOutput()
    {
        $this->requireProcessIsStarted(__FUNCTION__);
        $data = $this->getErrorOutput();
        $latest = substr($data, $this->incrementalErrorOutputOffset);
        if (false === $latest) {
            return '';
        }
        $this->incrementalErrorOutputOffset = strlen($data);
        return $latest;
    }