You want to record data submitted with the POST method, such as from a web form.
Generally not possible in Apache 1.3 unless the POST-handling module explicitly records the data; possible in Apache 2.0 via input filter functionality, but no such filters are available at the time of this writing.
In Version 1.3 of Apache, only one module receives the chance to process the message body of a request, which contains the POST variable settings, and it's up to this module to record them. The request information is read from the network exactly once by the module chosen by the server to handle the response, and therefore, the information isn't available to the logging phase, which follows the content handling phase.
For example, if you're using mod_perl, you may be able to record the information if the content handler that delivers the response is a Perl script being handled by mod_perl.