Have you seen this error on a cpanel server?
"Access Denied. Unable to establish a PHP session.The account must be able to write to the php session directory and must not exceed the assigned disk quota. If you believe that this is in error or inadvertent, contact your system administrator and ask them to review your server settings"
In some scenarios, this is just affecting one or few cpanel accounts. Meaning this is not a server wide issue. Let see how to fix that in a few steps:
1 . SSH into the server as root.
2. Check the permission and ownership of /home/$user/tmp folder. Set ownership as $user.
# chown $user:$user /home/$user/tmp
3. Set permission of the tmp folder to 755.
#chmod -R 755 /home/$user/tmp
4. Test now to see if PHPMyAdmin is working fine now…if the answer is no, go to next step….
5.Check to see if there is a file like /var/cpanel/overquota/blocks_$user and removed it.
6. rm /var/cpanel/overquota/blocks_$user
7. You should be ready to go.