Advanced Paytm/PhonePe Integration in PHP

# PHP Developer Needed: Paytm Merchant QR Payment Integration with PhonePe Deep Link and Payment Verification

## Project Overview

I am looking for an experienced PHP developer who can improve an existing PHP-based payment system that currently generates Paytm merchant QR codes and payment links.

The current system supports QR-code payments and Paytm intent links. I want to add **PhonePe payment initiation support and reliable server-side payment verification**, while maintaining compatibility with the existing payment flow.

I have an existing codebase and database structure. This is an integration and enhancement project, not a complete website development project.

## Current System

The existing system includes:

- PHP-based payment page.
- Paytm merchant details and UPI ID stored in the database.
- Dynamic QR code generation for a specific transaction amount.
- Paytm intent link generation.
- Order creation and transaction reference management.
- MySQL database integration.
- Payment status polling from the frontend.
- Existing Paytm transaction-status API integration.
- Order status updates and callback handling.

I can provide the relevant PHP files and database schema to the selected freelancer.

## Required Features

### 1. PhonePe Payment Link / Deep Link

- Implement a PhonePe payment button alongside the existing Paytm and QR payment options.
- Generate a suitable PhonePe-compatible payment deep link for the transaction.
- Pass the correct payee UPI ID, amount, transaction reference and payment note, as supported by the chosen integration method.
- Open the PhonePe app when installed and handle cases where the app is unavailable.
- Ensure the generated payment request works on supported Android devices.
- Do not use an undocumented or unsupported integration without explaining its limitations.

### 2. Payment Verification

This is the most important part of the project.

After a customer makes a payment through PhonePe, the system must determine whether the payment was actually successful.

Requirements:

- Verify payment status on the server, not merely from the frontend.
- Use an authorized merchant API, webhook, transaction-status API, or another legitimate and technically supported verification mechanism.
- Validate the transaction reference, amount, merchant details and transaction status.
- Prevent duplicate credits or duplicate order-success updates.
- Handle pending, failed, successful and delayed payments correctly.
- Ensure that simply opening a payment app or returning to the website does not mark an order as paid.

**Important:** I understand that generating a PhonePe deep link and independently verifying a UPI payment are two different tasks. Please explain how you would implement both.

### 3. Integration with Existing PHP Code

- Integrate the solution into my existing PHP and MySQL codebase.
- Preserve the existing Paytm payment flow.
- Avoid breaking existing QR-code payments or order processing.
- Follow the current database structure wherever possible.
- Add database changes only when necessary.
- Implement proper validation, error handling and transaction logging.

### 4. Testing and Documentation

The completed solution must include:

- Testing instructions for Android devices.
- Successful, failed, pending and duplicate-payment test scenarios.
- A clear explanation of the payment-verification mechanism.
- Instructions showing which files were modified and where the code should be deployed.
- A list of any required merchant API credentials, permissions or third-party services.

## Required Skills

- PHP and MySQL.
- UPI payment integration.
- Paytm merchant integration.
- PhonePe payment integration or relevant UPI deep-link experience.
- Server-side payment verification and webhooks.
- REST APIs, JSON and secure transaction processing.
- Debugging existing PHP applications.

## Before Applying

Please answer these questions in your proposal:

1. Have you previously implemented PhonePe or UPI payments in a PHP application? Briefly describe your experience.
2. How would you generate the PhonePe payment request while preserving the existing Paytm QR payment flow?
3. How would you independently verify a payment made through PhonePe?
4. Which authorized merchant API, webhook or transaction-status mechanism would you use, and what access would you need from me?
5. Can you work with my existing PHP codebase instead of rebuilding the payment system?

Please be transparent about any merchant-side permissions or API access required. I do not want a solution that only opens the PhonePe app without a reliable way to confirm the resulting payment.

## Deliverables

- Working PHP code integrated with the existing system.
- PhonePe payment initiation support.
- Server-side payment verification, where supported by the available authorized merchant integration.
- Preserved Paytm and QR payment functionality.
- Testing and deployment instructions.
- Brief technical documentation.

## Budget and Timeline

Please submit your estimated fixed price, delivery timeline and proposed implementation approach.

I am open to reasonable offers from developers who have genuine experience with payment integrations.

## Security Note

Merchant credentials, passwords, API keys, session cookies and other sensitive information will not be posted publicly. Any necessary access will be discussed securely after selecting a suitable freelancer.

Please apply only if you understand the difference between initiating a UPI payment and verifying the actual transaction.