University Woocommerce Store - Student Number Required on Checkout - wordpress

Question

I have built a Woocommerce store for a university client for the sole purpose of selling study tours to the students twice a year. Client is requesting that on check out (or on sign up) students are required to enter their student number and this number needs to be be approved in the WordPress or Woocommerce database before the system will let them continue.
There are about 100 students that can apply, so I can unload the individual student numbers if needed (no need to link to a secondary system if this makes things easier). The students can only order 1 item from the store, so the item needs to link to their student number and once the sale is made they can not order any other products from the store. I already added single lifetime purchases plugin, but this links to their email addresses and some students then use alternative email addresses to purchase more items when they are not allowed to. They only have 1 unique student number so it should rather link to this number.
I was thinking either:
A) Upload the active student numbers and on checkout verify the number is correct and hasn't been used already, or
B) Make the students register before they can access the site and have the system check the student number is valid before hand.
Can anyone point me in the right direction?

Answer 1

Hands down the best, and most optimal solution for this problem would be your B) choice. Forcing students to enter their student number when registering for the site would be the best option, since the ability to then compare the value saved to their profile with the value entered on checkout would be relatively easy on the front-end side.
I can help you out with a partial solution to your problem, and that's to give you a head start on what you can do hook onto the Woo-commerce registration form to create additional fields as required:
Note: this is an example of how to add Phone Number, First Name, and Last Name to the form.
function wooc_extra_register_fields() {?>
      <p class="form-row form-row-wide">
      <label for="reg_billing_phone"><?php _e( 'Phone', 'woocommerce' ); ?></label>
      <input type="text" class="input-text" name="billing_phone" id="reg_billing_phone" value="<?php esc_attr_e( $_POST['billing_phone'] ); ?>" />
      </p>
      <p class="form-row form-row-first">
      <label for="reg_billing_first_name"><?php _e( 'First name', 'woocommerce' ); ?><span class="required">*</span></label>
      <input type="text" class="input-text" name="billing_first_name" id="reg_billing_first_name" value="<?php if ( ! empty( $_POST['billing_first_name'] ) ) esc_attr_e( $_POST['billing_first_name'] ); ?>" />
      </p>
      <p class="form-row form-row-last">
      <label for="reg_billing_last_name"><?php _e( 'Last name', 'woocommerce' ); ?><span class="required">*</span></label>
      <input type="text" class="input-text" name="billing_last_name" id="reg_billing_last_name" value="<?php if ( ! empty( $_POST['billing_last_name'] ) ) esc_attr_e( $_POST['billing_last_name'] ); ?>" />
      </p>
      <div class="clear"></div>
      <?php
}
add_action( 'woocommerce_register_form_start', 'wooc_extra_register_fields' );
You can easily edit this code and change it to one added input, namely the student number which you're looking for. Hope this helps, good luck!