php - Debugging Drupal's White Screen of Death?

I have a Drupal installation that previously worked perfectly on my localhost. However, now, after a formatted my computer, it just shows a blank screen (completely white).

So my question is, how can I see where things are going wrong, if I can't even log into the sever?

The only errors I can find are (taken from the Apache Error Logs):

[Tue May 17 05:05:04 2011] [notice] Parent: child process exited with status 255 -- Restarting.
[Tue May 17 05:05:04 2011] [notice] Digest: generating secret for digest authentication ...
[Tue May 17 05:05:04 2011] [notice] Digest: done
[Tue May 17 05:05:07 2011] [notice] Apache/2.2.11 (Win32) DAV/2 mod_ssl/2.2.11 OpenSSL/0.9.8i PHP/5.2.9 configured -- resuming normal operations

[Tue May 17 05:05:07 2011] [notice] Server built: Dec 10 2008 00:10:06
[Tue May 17 05:05:07 2011] [notice] Parent: Created child process 6992

There are no errors in Watchdog...

I am using Xamp 1.7.1 (PHP 5.2) and Drupal 6.

I just also need to mention that once I try and load the site on my local machine, apache also crashes! I added this:

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

And it still just shows the screen of death? Where can I actually see errors?

I also found this in apache access.log:

127.0.0.1 - - [17/May/2011:05:22:14 +0200] "GET /greekmerchant/src/ HTTP/1.1" 200 3

127.0.0.1 - - [17/May/2011:05:25:45 +0200] "GET /greekmerchant/src/update.php HTTP/1.1" 302 -
127.0.0.1 - - [17/May/2011:05:25:46 +0200] "GET /greekmerchant/src/update.php?op=info HTTP/1.1" 200 -

... after trying to access update.php. It also just goes to a white screen.

I have this in my sql config file:

[mysqld]
port= 3306

socket= "C:/xampp/mysql/mysql.sock"
basedir="C:/xampp/mysql" 
tmpdir="C:/xampp/tmp" 
datadir="C:/xampp/mysql/data"
skip-locking
key_buffer = 16M
max_allowed_packet = 128M
table_cache = 64
sort_buffer_size = 512K
net_buffer_length = 8K

read_buffer_size = 256K
read_rnd_buffer_size = 512K
myisam_sort_buffer_size = 8M
log_error="mysql_error.log"

And...

[mysqldump]
quick

max_allowed_packet = 128M

Also, my PHP memory is set to 1024MB.

Anyone got any idea why this is just dying? Is it really a memory problem? What else can I do to get errors shown to me? I still see nothing even after enabling error logging.

Update:

The website runs on my local machine if I delete the files folder. So, for some reason, when it has to access files in the files folder, it runs out of memory. Why? Or better yet, what could be causing this excessive use of memory?

Answer

There is a whole page in the Drupal handbooks dedicated to debugging the "White Screen of Death". In a nutshell, enable error reporting by adding the following at the top of your index.php file:

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

...and check the logs, which you've already started to do. Those two steps tend to pinpoint the problem, most of the time. If that doesn't point you towards a solution, continue down the handbook page, for lots more tips.

If I had to take a wild guess, I would say your case is probably an out-of-memory error.