Debug message in PHP?

I am using PHP from past 4 year and used to debug my code using die and echo statement and will log the debug message in file if running backend job(Cron) while using PHP 4 and then we started using Zend Framework and use Zend_log. But for those who won't use Zend Framework here is the function which will be useful in debug debug_backtrace this function is available from PHP4 didn't know i just came to know while i was browsing php.net, This information is for user like me who didn't know about it :)