Quite often there are situations where conventional logging, which writes the apache webserver is not enough. For example, your site is hacked, and you learn a web server logs in order to nahodzheniya hole in your site. If you know the exact time hacking, it is likely that you will find in the logs or script file that was accessed from the POST request. Yes, this will be a POST request. But the trouble is that you will see in the log file only, and that's exactly what he was told, seen unfortunately will not. And the exact time hacking rarely known, so it is usually to find a hole on the website through which it was hacked, very difficult.