Thanks John for getting back to me.
I am trying to interact with existed forms that available in Omeka, e.g user form and exhibit builder metadata form, and finally config form. I am new to Zend and MVC model and the way to interact with existing form from my plugin is different than the way I vision it.
What I am trying to do with config form is save some information about what group the exhibit belong to e.g. I thought to save this information into the theme-options field available with each exhibit instead of creating a table in db for this purpose.
So it works perfect every time a user save an exhibit I check in my plugin after save hook and update the theme option with the name of the group if it is not available.
The problem happen if the user decide to visit the config form then the data in the theme options are wiped up by exhibit builder and it reads the new data from the $post. Ofcourse the group name is not available in the post and in config.ini file I do not have a solt for the group name, so it wipes the group name from the theme option. to save the group name to theme option the user has to go back to exhibit meta data page and click on save which will trigger the after save hook.
I guess I have two options now:
either I save the group name at the init hook as you suggest or create a table in db to save the exhibit id and group name and id...ect.
I did that successfully when I want to link each user with group. but I though to use the theme option in exhibit builder to save some time.
if you have a third option please let me know.
I same similar problem when I try to store an image for each exhibit to be displayed next to the exhibit title. I store it in theme options.
I wonder if this something should be added to Exhibit builder plugin in the future since I saw other people trying to add extra data to exhibit builder without a need to update the exhibit builder code and adding any new colums to exhibit builder db tables.