How to modify an old plugin for 2.1
So you found and old plugin but it does not work with your version of Vanilla....
There are some modifications you need to make. Some will work others will not due to major changes in framework. These 3 steps cover only the basic changes for a plugin that is 2.0 but 2.1 friendly . This means it requires only minor changes to work.
1.If your old plugin's definition has a lower version requirement. You must remove the entire requirement sentence from the list.
2.If your old plugin says: class OldPlugin implements Gdn_IPlugin you must change that to: class OldPlugin extends Gdn_Plugin
3.If your old plugin contains: &$Sender You must change it to this: $Sender
If these changes still don't make it work there are a couple other changes you can make to the Handlers that render the plugin. These simply tell where it will appear.
If these functions exist , example:
Not every plugin will work for 2.1 even given these changes, just as not every 2.1 plugin will work for 2.0.
Because of extensive changes in the framework and additions to it that do not exist in 2.0, those plugins will only work with their intended versions.
Before you test your fixed plugin, make sure you backed up all your plugins and files. Or test it under a test environment to minimize any potential risk.