Upgrading phpMyAdmin
Normally, upgrading is just a matter of installing the newer version into a separate directory and copying the previous version's config.inc.php to the new directory.
Note
An upgrade path or the first-installation path, which should not be taken, is to copy libraries/config.default.php to config.inc.php. This is because the default configuration file is version-specific, and is not guaranteed to work for the future versions.
New parameters appear from version to version. They are documented in Documentation.html and defined in libraries/config.default.php. If a configuration parameter is not present in config.inc.php, its value from libraries/config.default.php will be used. Therefore, we do not have to include it in config.inc.php if the default value suits us.
Special care must be taken to propagate the changes we might have made to the layout.inc.php files depending on the themes used. We will have to copy our custom themes sub-directories if we added our own themes to the structure.
