Elefant has a simple, built-in way for apps to be installed and upgraded, which can also be used for easy database migrations. Here's how it works:
There is an apps table that manages the installed version of an app.
In the [Admin] block of an app's conf/config.php file, you can specify an install and upgrade handlers, and a version number, like this:
[Admin]
name = App Name
handler = myapp/admin
install = myapp/install
upgrade = myapp/upgrade
version = 1.0-stable
The Admin > Tools menu uses the above info to notify admins when new apps are found in the apps folder, and when app versions have been changed by overwriting an app with a new version. It will highlight the new app and add either (click to install) or (click to upgrade) to its menu item.
The controller has two methods for developers to use in their install and upgrade handlers:
installed ('appname', $appconf['Admin']['version']); ?>$version will be true if it's already installed, false if it hasn't been, or will contain the currently installed version number if a previous version has been installed.
<?php
$this->mark_installed ('appname', $appconf['Admin']['version']);
?>
This will save the current version to the apps table so Elefant knows the app is now installed and current.
Here's a link to a sample app that makes use of the above features:
http://github.com/jbroadway/installtest
Developers can use this as an example or a template for your own install and upgrade handlers.