O Guia Definitivo do Yii 1.1

Info: Message routing occurs at the end of the current request cycle when the
onEndRequest event is raised. To explicitly terminate the processing of the current
request, call CApplication::end() instead of die() or exit(), because CApplication::end()
will raise the onEndRequest event so that the messages can be properly logged.
Message Filtering
As we mentioned, messages can be filtered according to their levels and categories before
they are sent long a log route. This is done by setting the levels and categories properties
of the corresponding log route. Multiple levels or categories should be concatenated by
commas.
Because message categories are in the format of xxx.yyy.zzz, we may treat them as a
category hierarchy. In particular, we say xxx is the parent of xxx.yyy which is the parent of
xxx.yyy.zzz. We can then usexxx.* to represent category xxx and all its child and
grandchild categories.
Logging Context Information
Starting from version 1.0.6, we can specify to log additional context information, such as
PHP predefined variables (e.g. $_GET, $_SERVER), session ID, user name, etc. This is
accomplished by specifying the CLogRoute::filter property of a log route to be a suitable
log filter.
The framework comes with the convenient CLogFilter that may be used as the needed log
filter in most cases. By default, CLogFilter will log a message with variables like $_GET,
$_SERVER which often contains valuable system context information. CLogFilter can also
be configured to prefix each logged message with session ID, username, etc., which may
greatly simplifying the global search when we are checking the numerous logged
messages.
The following configuration shows how to enable logging context information. Note that
each log route may have its own log filter. And by default, a log route does not have a log
filter.