This function is a wrapper for Apache's table_get and table_set. It
edits the table of notes that exists during a request. The table's
purpose is to allow Apache modules to communicate. Here are some
further details I found in the mailing list archives:
<P>
Rasmus wrote:
<P>
The main use for apache_note() is to pass information
from one module to another within the same request. I haven`t seen an
actual implementation that uses this yet, but it is quite possible for
someone to write a module which performs some sort of action at one of the
other stages of the request and stores some information in the Apache note
table which will then be available to PHP when the request reaches the
content-handling stage. Or, one could have a logging module that reads
something from the Apache Note table set by PHP.
<P>
David Sklar wrote:
<P>You can use it to facilitate communication between modules that act on the
request at different stages. I use it to record userids in logfiles. In
some PHP that gets auto_prepend-ed, I do a
<P>
apache_note(`sessionID`,$sessionID);
<P>
(where $sessionID has been slurped out of a cookie and processed)
<P>
and then, in my httpd.conf, part of my LogFormat is
<P>
"%{sessionID}n"
<P>
so that sessionID gets written to the logfile.
<P>
If you have other modules that process the request before or after PHP
does (authentication, fixups, whatever..) you can have them talk to PHP or
PHP talk to them through the notes table.