Are you getting below error during phpmyadmin access in cPanel ?

Access Denied Unable to establish a PHP session. If you believe that this is in error or inadvertent, contact your system administrator and ask them to review your server settings.

Usually, this error comes when the permission or ownership of the tmp folder for this user is wrong or tmp directory not exist under /home/$cpaneluser. Make sure that ownership of /home/$cpaneluser/tmp folder has set to $cpaneluser and permission as 755. If it is not, you will face the same problem.

Resolution: 

Login to cPanel go to file manager and under /home/$cpaneluser/ you will see tmp directory try to change  permission to 0755. If this directory not exist so you can create this directory and set permission 0755. If you able    to do this changes and phpmyadmin is accessible or if you getting same error so you need follow below steps.

Login to your server via SSH as root.

Check the permission and ownership of /home/$cpaneluser/tmp folder. Set ownership as $cpaneluser

 #chown $cpaneluser. /home/$user/tmp

Set permission of the tmp folder to 755.

 #chmod 755 /home/$cpaneluser/tmp

Now you  resolved this issue. Please note that you need to remove $cpaneluser with your cpanel username.