Do you disable any PHP functions on your Linux hosting accounts?
To change the status of a function, you can use custom initialization (
php5.ini) files. For more information, see What filename does my PHP initialization file need to use?
Disabling APC on Your Hosting Account
Why isn't my PHP initialization file taking effect?
Too many files in one folder? Try a dirtree.
What filename does my PHP initialization file need to use?
Enabling PHP Modules on Your Shared Hosting Account
What do I do when I receive a PHP header error message?