CartThrob Gift Certificates Add to Cart form causing fatal error

Question

I just purchased the Gift Certificates plugin yesterday and am setting up the Add to Cart form today. Here is the current version of the tag:

{exp:cartthrob_gift_certificates:add_to_cart_form return="shop/cart" on_the_fly="yes" allow_user_price="yes" shipping_exempt="yes"}
    <label for='price'>Price</label>
    <select name='price' id='price' />
        <option value="25">$25</option>
        <option value="50">$50</option>
        <option value="100">$100</option>
        <option value="250">$250</option>
        <option value="500">$500</option>
        <option value="1000">$1000</option>
    </select>

    <label for='gift_certificate_email_address'>Recipient Email Address</label>
    <input type="text" value="" name="gift_certificate_email_address" id="gift_certificate_email_address" />

    <label for='gift_certificate_note'>Note</label>
    <input type="text" value="" name="gift_certificate_note" id="gift_certificate_note" />

    <div class="control-group full">
        <div class="form-actions">
            <input class="add-cart" type="submit" value="Add to Cart">
        </div>
    </div>

{/exp:cartthrob_gift_certificates:add_to_cart_form}

This is currently causing the following fatal error:

There is an older forum post that lists another fatal error in a different file, but references sort of the same situation (I was looking for how to let the user choose the price for the gift certificate).

Does anyone know what is causing this error?

EE 2.8.0

CartThrob Pro 2.6

CartThrob Gift Certificates 1.25

I also have CartThrob Credits 1.21 installed if that plays a factor.

Answer 1

Spoke to Mr. Barrett at CartThrob on a support call for a separate issue and I mentioned this problem I was having. He had me replace the gift certificates add to cart form tag

{exp:cartthrob_gift_certificates:add_to_cart_form}

with the standard cartthrob form tag, but adding in a gift_certificate="yes" parameter

{exp:cartthrob:add_to_cart_form gift_certificate="yes"}

This has resolved my issue.