What are some guidelines for maintaining responsible session security with PHP? There's information all over the web and it's about time it all landed in one place!
Check the permission of the folder and of its parents. It shouldn't be public (/tmp) or be accessible by other websites on your shared server.
Assuming you still want to use php session, You can set php to use an other folder by changing _session.save_path_ or save the data in the database by changing _session.save_handler_ .