Been trying to learn howto extend plugins. I find no HOWTO that directly addresses "Extending an Existing Plugin". I did find these howtos, which give some principles, but no howto is directly addressed:
I'm sure to the writers these are clear, assume nothing and have logical flow, but in fact they assume so much that none of these make any sense at all, to those actually trying to learn. I think these are some of the most prime examples of ambiguity.
Example in the "Add Methods", from the first link, they throw out these commands as though they are something issued from either a command (can not be for a browser app) or some command api interfaces where the commands can be interactively issued, but one finds there is no such interface in WP, and studying other plugins, one finds all have a "wp-install.php" file, not mentioned in any of these helps, that all these commands go in and which is uses to actually install the plugin or any extensions to an existing plugin.
Also what is left out, is there is a group of files, still do not have an accurate list of them, that are required before the plugin, or plugin extension is recognized and allowed to be seen within the "PlugIN" admin option set, so until the list is correct, you will not be able to execute any install to get the plugin installed. Futher confusion comes, as what I read the list of files is different for a stand alone plugin than for a plugin extension.
The problem I'm finding is both in what goes into the install file and how are the files and directories organized to work.
IN my case, I have a plugin that needs to be extended where I must add 3 pages to the admin side to set values in the 6 new database tables, then allow the user to choose the old forms, from the original plugin, or the new forms from the extension, where the new allow assignments and cross table linking that is not available in the old plugin.
The new forms, as I understand WP standards, must have the same name as the original forms, but will reside in the directories under the home directory assigned to the plugin extension. A simple set of exclusive check boxes on the admin side should show which set of forms are being used.
Hope there really is a good howto out there on this, but I can not find it.
Also I tried posting on the main WP Forums and got no response at all on this.