Reordering field groups in Advanced Custom Fields

When you add field_groups to acf_form() you expect that the field groups will be added in the order you add them to your field_groups array. For example:

acf_form(array('field_groups' => array(604, 142));

This should display group 604 and 142, in that order. Unfortunately it doesn’t. So we need to figure out how to reorder fields. Digging around the code I found the get_field_groups hook which we can use for this.

Example code:

add_filter('acf/get_field_groups' , 'theme_reorder_field_groups');
function theme_reorder_field_groups($field_groups)
{
    $temporary_field_groups = array();

    //Put all groups in new indexed array
    foreach($field_groups as $field_group)
        $temporary_field_groups[$field_group['id']] = $field_group;

    //Identify if it's our specific ACF form by its field groups
    //In our case we have a form with the field group ids 142 and 604,
    //So we only want this code to run for that specific form
    if(array_key_exists(142, $temporary_field_groups) && array_key_exists(604, $temporary_field_groups))
    {
        $new_field_group = array();

        //Reorder the fields. The fields will appear in the order they are added to the $new_field_group array
        $new_field_group[] = $temporary_field_groups[604];
        $new_field_group[] = $temporary_field_groups[142];

        return $new_field_group;
    }

    return $field_groups;
}

Note: Since there is no way to uniquely identify the form, we are settling with only using the reordering code if we can find both of our field groups.