vi /etc/phpmyadmin/config.inc.php

If you want to change the 'login cookie validity' in configuration file, then open the phpmMyAdmin configuration file, config.inc.php in the root directory of PHPMyAdmin.(root directory is usually /etc/phpmyadmin/)

After locating the config.inc.php , search for the line below and set it to the value of seconds you want phpmyadmin to timeout:

$cfg['LoginCookieValidity'] 

or

Add the following:

$cfg[ ' Servers'] [$i] [ ' LoginCookieValidity' ] = <your_new_timeout>;

For example:

$cfg[ ' Servers'] [$i] [ ' LoginCookieValidity' ] = <3600 * 3 >;

The Timeout is set to 3 Hours from the Example above.

session.gc_maxlifetime might limit session validity and if the session is lost, the login cookie is also invalidated. So, we may need to set the session.gc_maxlifetime in php.ini configuration file(file location is /etc/php5 /apache2/php.ini in ubuntu).

session.gc_maxlifetime = 3600 * 3