Dolphin forms - multiplyable - select_multiple

I am trying to gain some understanding of Dolphin forms.  The only info I can find on forms is the wiki for Dolphin 8 forms and some of that does not apply to Dolphin 7.  I am working on a form and  I used the following to set up to be able to add an additional selection.

'attrs' => array (
                        'multiplyable' => 'true', 
                        'add_other' => 'false',
                        'add_text' => 'false',
                     ),
                    'db' => array (
                        'pass' => 'Categories',
                    ),

I could add a second select to the form; however, only the second select would be added to the database.  What did I do wrong?

I could not figure this out from reading and examining existing code so I changed over to use a select_multiple type and it works, all selections are stored in the database.  I just liked the cleaner look of the first method but working is what is desirable although I would like to learn why the first is not working.  What am I missing with the first method.

I am not sure I follow what you are asking but in order to replicate the same select box so multiple options can be chosen you would use the code snippet you posted plus the type of element must be select_box not select

Thanks Modzzz, looking back at my code, it was set to just select.  I don't see select_box in the Dolphin 8 forms Wiki; is there one for working with Dolphin 7 that you can point me to?  I waste so much time trying to hunt this stuff down.

Yes, working as it should and it is returning the values when returning to the form for editing.  If I had just known about select_box a few hours ago, I would be much further alone.

not sure why some disss her. She's learning quite a LOT more than I can step up into linux world. I don't know how old she is but she got more motiviation than I do and willing to share. (exception for deano). 

I just learn something new.  Earlier I asked about getting the membership of a member and then I mention getMemberMembershipInfo().  I thought that function returned the membership ID.  That function actually returns an array that contains the ID and the Name; so to get the membership ID, you need to address it as array[ID]; I had a function that kept failing and that was the reason.  More wasted time.  It would be nice to have some documentation on the functions and classes.  I should start keeping a notebook.

As an FYI - what I do for functions: if I see a function and not sure what it does, I do a search for that function throughout the site. (I use Dreamweaver so it is pretty fast and accurate). Most of the functions are on a page in the inc folder I have found so far, except for those specific to modules. Once the function is found dissecting what it does is usually not too hard.