Safecracker entry form, specifying categories across multiple pages

Question

I have a multiple page Safecracker form, as there are a number of large category groups that need to be chosen from. On Page 2, I have a content type select. On Page 3, I have a topic select. And, on Page 4, I have a number of selects to reference syllabus documents.

The select fields look like this, that is the categories shown are being filtered by group_id:

<select name="category[]" id="select_syll-ac" multiple="multiple" class="multiselect">
          {categories group_id="17"}
                  <option value="{category_id}"{selected}>{category_name}</option>
          {/categories}
</select>

Currently, only the options selected on Page 4 are making it to the final entry. I thought that previously the options selected on page 2 were also being retained.

preserve_checkboxes=“yes” does not fix the behaviour.

Given Pages 2, 3 and 4 are all dealing with categories, do I have to add a hidden select of the category groups on Page 2 and 3 to Page 4?

Answer 1

You probably need to output the already checked categories in order to preserve the selection. You can output those categories in hidden fields in each pages:

{categories}
{if '{selected}' != ''}<input type="hidden" name="category[]" value="{category_id}" />{/if}
{/categories}

otherwise, on each submit containing the field category[], the categories will be reset to the new form values.