I've tried multiple methods of changing a category from option 1 to option 2 and none of them are working properly.
$item = PodioItem::get_basic($ItemID);
$field_id = 'print-to-pdf';
$item->fields[$field_id]->values = 2;
(this is the simplest version, following the API documentation. The category doesn't change. $ItemID is retrieved from the original POST and is correct)
PodioItem::update($ItemID, array('fields' => array("print-to-pdf" => array('id' => 2))));
(This is typically used for updating multiple fields but can be used for one as well, doesn't work.)
PodioItemField::update( $ItemID, $FieldID, array(), array(2));
(This one I've used to successfully update raw data fields, but it isn't working for categories.)
Could I get some help here?