HTML / Php forms - how to save an optional, unselected drop-down as null/empty instead of an option?

Question

I'm building forms for Drupal 6 through the cTools wizard (which is primarily php), and I have a few select boxes that are optional. I have my options set up like so:

0|Select

1|option 1

2|option 2

3|option 3

4|option 4

Or on some, like a year or state select, I'm using array_unshift to append a "Select" to the front of a list that is built dynamically or referenced from elsewhere.

When there is no user input, these select boxes return values of "Select", 0, or -1 when I want them to return nothing at all.

I'm pretty new to PHP, so I'm probably not asking this in the right way because I haven't found anything at all about what seems like it should be a fairly common issue. Anyone have any idea how do to this, or how to better phrase my issue to find answers? Thanks!

Answer 1

Because the field gets posted, you will always receive a string value of some sort in $_POST. I normally provide a blank value (<option value="">Select</option>) which gives me a blank string on the PHP side. You can then (if you don't mind casting "0" -> false) do something like

<?php if(!$_POST['field']) $_POST['field'] = null; ?>

to null out that value.