Populating a hidden field based on dropdown selection

Hello,

I have created a dropdown, and I want to pass the value that's selected to a hidden field when it's submitted.

Basically the form is used for submitted an advert, the dropdown is the number of images they require in the ad (options are 1-5), and the more images they submit, the higher they need to be in the listings. The dropdown is also a pricing field, which passes the value to the total. I just need to pass the dropdowns value to a hidden custom field, which is used to order the posts on the output page.

Can anyone offer some advice on what I need to do?

Thanks!

Hi Carl

Thanks for getting back to me. Unfortunately I'm pretty new to php so I am trying to work though the example you gave.

I have amended the example to select the specific form, how to I format it so that I take the value from the dropdown and populate it into the hidden custom field? Is "Blender Version:" in the example the source (dropdown in my case)?

Thanks

Thanks Carl.

So rather than using a hidden field, I just need to send the value of the dropdown to the required custom field?
I've changed the values of the example you directed me to, but haven't managed to get it to work. It looks like this so far:

add_action("gform_post_submission", "add_custom_field", 10, 2);
function add_custom_field($entry, $form){
    //NOTE: replace 1 with the ID of your form.
    if($form["id"] != 9)
       return;

    //getting post meta
    $meta = get_post_meta($entry["post_id"], 'key', true);

    //updating price property of array.
    //NOTE: replace "1" with the ID of the field you want to populate the price field.
    $meta["ranking"] = $entry["30"];

    //updating meta
    update_post_meta($entry["post_id"], "key", $meta);

}

Thanks, sorry PHP isn't my strong point!