Automated GST E-Invoice Upload

My custom-built billing cart (PHP with a MySQL back end) already generates the IRN-ready JSON for every sale. What I still lack is an automated way to place that file on the Government GST e-invoice portal without the extra OTP step that normally interrupts the flow.

Here is exactly what I want the new script to do:

• Log in to the e-invoice portal using my registered user-ID and password only, maintaining an authenticated session until all queued invoices are processed.
• Pick up each freshly generated invoice JSON from the billing cart database/folder, validate the basic schema, then upload it.
• Capture the acknowledgment details returned by the portal (IRN, Ack No., Ack Date, QR code string) and write them back to the corresponding order record in MySQL.
• Handle session expiry or CAPTCHA in a resilient way so uploads resume automatically.
• Enforce user authentication for anyone who might manually trigger or configure the script; no OTP should be required once the service credentials are stored securely.

Please build this as an automated script rather than a manual or API-only solution; language is flexible as long as it slots cleanly into the existing PHP/MySQL stack and can run on a Linux server. Deliverables are the fully commented source code, a brief setup guide, and a short remote demo showing one live invoice travelling end-to-end.