Joomla! site pains and the solutions that worked for me: “Error 500”, “Error 404.2” - The White Screen of Death

I was playing around and trying to turn on a SEF module in Joomla! then everything stopped working :(
Not sure if the SEF and the problems were related, but my Joomla! site gave errors and even showed blank pages (white screen of death).
It seemed like some files were not accessible so I tried to change the file permissions but that didn’t help - “500 'SITE CHMOD 777 modules': command not understood”.  Seemed like that’s correct when running on Microsoft IIS (version 6).

I then thought that these files were the problem since I couldn’t open them: .htaccess .htgroup and .htpasswd


The I asked the webmaster to check the site and he found a problem: “each site running PHP has to have a specific mapping to the php5isapi.dll file and for some reason, this was changed to point to the php.exe file. ”

Here’s a nice article that helped check the settings on IIS 6: How To Install PHP on IIS 6.0 

I have found a way of turning on error logging on the index page’s screen (from “The White Screen of Death (Completely Blank Page)”
Just temporarily edit your index.php file (normally located in your Joomla! root directory) directly after the first opening PHP tag to add the following:
===============
<?php

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

===============

I’ve turned it on and I think this will give clues as to what’s going on.  So far there’s a file that’s not accessible – now to contact the web master to see what’s going on with that file’s accessibility



Are you a ZenCart page designer?
Turning on error logging for ZenCart php would also save lots of time: enable_error_logging.php
Extracted from: Debug Error-Logging Utility for PHP and Zen Cart:

Installing the debug error-logging tool will create debug logs of PHP problems for you to review.
Be sure to remove the utility when not needed, or it will slow down your site and consume large amounts of disk space.

** HOW TO USE: **
1. Download and unzip the utility
2. Upload the enclosed enable_error_logging.php file to the /includes/extra_configures/ folder.
3. Test the page on your site that is having problems -- ie: trigger whatever symptom is ailing you.
4. Open the latest log file /cache/myDEBUG-xxxxxxx.log to see the list of any PHP errors that occurred while the page/test was running.
5. Be sure to delete the enable_error_logging.php file from the /includes/extra_configures folder when done (or rename it to .php1 instead of .php )

Update on 28Mar2010:
If you are getting errors trying to integrate ZenCart with PayPal’s express checkout: error “10413 Transaction refused because of an invalid argument. See additional error messages for details. - The totals of the cart item amounts do not match order amounts.”  See here for how to solve it by modifying the paypalwpp.php file: Configuring ZenCart and PayPal: Error 10413 solved