Error in phpMyAdmin after updating to v4.8.0: The $cfg['TempDir'] (./tmp/) is not accessible
Solution was to create a folder called tmp like this: /usr/share/phpmyadmin/tmp.
Also make sure that the user (or group) running the webserver (e.g. Apache) has write access to the newly created tmp folder. Consequently, change the ownership to that user or add write access for all users. The latter one might not be really advisable.
simple fix is to create tmp dir in your phpmyadmin dir and set permission to 777
mkdir tmp && chmod 777 tmp
then
update your config.inc.php file add that line
$cfg['TempDir'] = 'tmp';