validating custom field during account creation

[ktrovato]

I have added a custom field to my create account page for a referral code. The field is manditory and produces an appropriate message. I also have a table in the database that I will store referral codes. I need the create account page to check and see if the referral code is correct based on the information stored in the db table.
Any help would be appreciated.

[ruanchao]

1. Click on Configuration > Customer Details to access the common Customer Details screen.

At the bottom of this page, you'll see 'Customers Referral Status', edit it.

Customers Referral Code is created from
0= Off
1= 1st Discount Coupon Code used
2= Customer can add during create account or edit if blank

NOTE: Once the Customers Referral Code has been set it can only be changed in the Admin Customer
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When new user create account, it will submit its referral code to 'create_account.php' which is under '\includes\modules\' folder. In the create_account.php file, you can query one of your tables which stores the defined referral code to match the $_POST['customers_referral'], and validate it.