Problem is that the backend webserver, apache2 or nginx doesn’t even know it’s running behind another software.
PhpMyAdmin tries to be “smart” and figure out its absolute URL and I run the apache2 or nginx backend on port 80.
The solution is to force an URL.
Add the following line to “config.inc.php“, changing the obvious:
$cfg['PmaAbsoluteUri'] = 'http://yourdomain.com/phpmyadmin/';