PHP is showing 'Use of undefined constant action Notice:' type messages when running install.php
It looks like you have Notices turned on in your PHP php.ini file.
This occurs when you first install php on your server, and the notices are
turned on by default.
(php.ini file is not a part of the script, but a part of PHP, where your PHP is configured)
Notices should always be turned off on production environments.
Edit your php.ini file and make sure that the error_reporting directive
is set to:
error_reporting = E_ALL & ~E_NOTICE & ~E_STRICT
Please make sure to restart your web server after editing the php.ini file.