How to get good stacktraces for exceptions
Event Timeline
I can confirm that, if an exception is thrown from phorge, a very nice stack trace will be spawned in the default webserver error log, with or without developer mode, as default.
The problem is, where is your PHP error log file?
Can you post the configuration of your apache HTTPd VirtualHost?
I suspect that you are using php_fpm instead of mod_php. So, errors are not in the Apache HTTPd error log file, but in something separated (like the PHP FPM pool, somewhere in your distro).
Feel free to update the question to add these details
@valerio.bozzolan: Thanks for solving this mystery! You were correct that php-fpm is installed. My <VirtualHost> entry in /etc/httpd/conf/httpd.conf defines ErrorLog /var/log/httpd/error_log. But the PHP stacktraces are in /var/log/php-fpm/www-error.log - I found them now.