Multi-select does not retain value after post in codeigniter

Question

I have a form in my application with a multi select. I'm using CI's form helper to build my forms, so the build of the element looks like this:

return form_multiselect('authors[response][]', $faculty->get_all_for_multiselect(), 
                         $pre_selected, $additional_attributes);

This is all well and good if the items are in the database ($pre_selected gets existing responses). However, I'm also running the form through CI's form validation, and when that happens, if validation fails, then the multi select loses the values that had been selected.

I'm sure this is something simple that I'm just over looking, so hopefully someone can help me out here.

Adding more information

The field is marked as required so it is going through the validator (although it will always pass as I'm automatically selecting the current user).

Answer 1

(I'm assuming $pre_selected is an array of values?)

You can reset selected values after failed form submit using the $_POST array.

Since you're already using $pre_selected, you should be able to use the following:

return form_multiselect('authors[response][]', $faculty->get_all_for_multiselect(), 
                         array_unique(array_merge($pre_selected, $_POST['response'])), $additional_attributes);