think\Process::getIncrementalOutput PHP Method

    public function getIncrementalOutput()
    {
        $this->requireProcessIsStarted(__FUNCTION__);
        $data = $this->getOutput();
        $latest = substr($data, $this->incrementalOutputOffset);
        if (false === $latest) {
            return '';
        }
        $this->incrementalOutputOffset = strlen($data);
        return $latest;
    }