Increase memory in your php.ini
While Drupal core will run with 8 MB of memory configured for your server, you may need to increase this depending on how may modules you use on your site.
In Drupal 4.7.x and below, when you go into ?q=admin/modules, you may experience a blank screen. This is caused by Drupal loading all the modules of your site into memory, whether you have them turned on or not. If you get a blank screen here, you have two choices; increase your allocated memory for PHP or delete unused modules.
In Drupal 5.x and above, this problem has been fixed, and the modules page no longer loads all modules. If you are still getting out of memory problems, you should either reduce the number of modules used or increase your allocated memory for PHP.
Depending on your host, this can be done in a number of places with the most likely being php.ini or .htaccess depending on your hosting situation.
Add for example:
memory_limit = 12Mto your php.ini file (recommended, if you have access)ini_set('memory_limit', '12M');to your sites/default/settings.php filephp_value memory_limit 12Mto your .htaccess file in the Drupal root
You will need to experiment with the value that is right for you depending on which modules you are using. Some people find they need to set the memory to 24M or higher.
NOTE: Some hosts do not allow you to control how much PHP memory is available. In this case you will need to work with your host, be very conservative with your module selection and testing or look for a new host that allows more flexibility.
If you are using Gallery2
I ran into blank pages with Gallery2 embedded in Drupal. After upgrading, I got blank pages in gallery in albums with lots of pictures.
I followed this; adding a line to the GALLERY code (please see link for exactly where and what) helped me. :)
Anisa.
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Kindness builds stronger bonds than necessity.
www.animecards.org - 18,000 card scans and counting!
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Admin page Blank
My entire Admin node/page went blank after installing a new module. Since I have no php.ini access, I changed my .htaccess to:
php_value upload_max_filesize 10M
php_value post_max_size 20M
php_value memory_limit 18M
I had to increase the php_value memory_limit to 18M before my Admin node came back. I also added:
ini_set('memory_limit', '18M'); (to the settings.php page as described above.)
So for everything is running ok now!
XAMPP / Windows
I'm developing locally using XAMPP / Windows XP, and I followed these instructions when Imagecache was having trouble with very large images (> ~2000px) being uploaded (it just couldn't process them at all). I didn't want to constrain resolution for my image content type (the images are used for high-resolution press kits as well as for normal web images).
At first I tried increasing my memory limit to 12M, then 32M and even up to 100M. As a last ditch effort, I tried 512M and now it works like a charm. Just wanted to comment so people might be able to avoid frustration by trying a much higher memory limit than you might expect you need (and this article implies).