Problem Description
This is caused by default permissions on a PHP installation not behaving nicely with PHP running under FastCGI. When you attempt to login to a PHP application (WordPress, Joomla, etc), it creates a PHP session to manage the cookie. These sessions are held in a randomly named file in /var/lib/php/session which has the permissions of user root and group apache. When PHP is running as a normal Apache module, it runs under the 'apache' owner (and apache group) on our CentOS servers. When it is running via FastCGI it is using the username of the FTP account for the domain being accessed and the group 'psacln'. This means that when it tries to create a session file in /var/lib/php/session, it fails because that directory is owned by root:apache -- it has no permission to create the session file.
Steps to Repair
This is repaired by changing the ownership of the /var/lib/php/session directory. Run the following command to fix this issue:
chown apache:psacln /var/lib/php/session
This will ensure that both the apache user and all members of the psacln group (all domains) have access to create their session files within this directory. When a session can be created, then users can once again login to their installed PHP applications.
