TIGER
Hi, I have read the TXT file, and I know exactly what you want. You want to save API calls by validating the user input (whether an account under that username exists or not). You are right, this can be achieved via API for fast response time, but it can be also be done by PHP header checking.
I will be using a custom PHP file to validate data to avoid any XSS attacks on the form.
Regards,
Adam A.