Recipe 8.25 Communicating Within Apache
8.25.1 Problem
You want to communicate from PHP to
other parts of the Apache request process. This includes setting
variables in the
access_log.
8.25.2 Solution
Use apache_note( ):
// get value
$session = apache_note('session');
// set value
apache_note('session', $session);
8.25.3 Discussion
When Apache processes a request from a client, it goes through a
series of steps; PHP plays only one part in the entire chain. Apache
also remaps URLs, authenticates users, logs requests, and more. While
processing a request, each handler has access to a set of key/value
pairs called the notes table. The
apache_note( ) function provides access to the
notes table to retrieve information set by handlers earlier on in the
process and leave information for handlers later on.
For example, if you use the
session module to track users and
preserve variables across requests, you can integrate this with your
log file analysis so you can determine the average number of page
views per user. Use apache_note( ) in combination
with the logging module to write the session ID directly to the
access_log for each request:
// retrieve the session ID and add it to Apache's notes table
apache_note('session_id', session_id( ));
Then, modify your httpd.conf file
to add this string to your LogFormat:
%{session_id}n
The trailing n tells Apache to use a variable
stored in its notes table by another module.
If PHP is built with the --enable-memory-limit
configuration option, it stores the peak memory usage of each request
in a note called mod_php_memory_usage. Add the
memory usage information to a LogFormat with:
%{mod_php_memory_usage}n
8.25.4 See Also
Documentation on apache_note( ) at
http://www.php.net/apache-note; information on
logging in Apache at
http://httpd.apache.org/docs/mod/mod_log_config.html.
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