UPDATE: for the drupal 6 version, please go here.

if your career as a developer has included a stay in the j2ee world, then when you arrived at drupal one of your initial questions was "where's the log file?". eventually, someone told you about the watchdog table. you decided to try that for about five minutes, and then were reduced to using a combination of <pre> and print_r to scrawl debug data across your web browser.

when you tired of that, you learned a little php, did a little web research and discovered the PEAR log package and debug_backtrace(). the former is comfortably reminiscent of good old log4j and the latter finally gave you the stacktrace you'd been yearning for. still, separately, neither gave you quite what you were looking for : a log file in which every entry includes the filename and line number from which the log message originated. put them together though, and you've got log4drupal

log4drupal is a simple api that writes messages to a log file. each message is tagged with a particular log priority level (debug, info, warn, error or emergency) and you may also set the overall log threshold for your system. only messages with a priority level above your system threshold are actually printed to your log file. the system threshold may changed at any time, using the log4drupal administrative interface. you may also specify whether or not a full stack trace is included with every message. by default, a stack trace is included for messages with a priority of error and above. the administrative options are illustrated below :

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