PHP Payment Gateway Integration Module
Employer
Dmytro Koval (demo account)
Project parameters
Type of cooperationOne-time project
SectionWeb development
Prepaymentwithout prepayment
Payment methodsCash, Bank transfer
Acceptance of requestsfrom today, 13:12 until Aug 28, 2026
Project description
Building a reliable payment gateway integration demands far more than calling a few API endpoints — it requires careful attention to security, idempotency, error recovery, and the edge cases that can affect every single transaction your business processes. Our web platform serves thousands of active users monthly, and as we expand our product catalogue we need a standalone, well-architected PHP module that can be embedded into any subsystem without introducing technical debt or opening security gaps. Familiarity with PCI-DSS awareness, OWASP secure coding guidelines, and webhook reliability patterns is essential for this project.
The module must cover the complete payment lifecycle: initiating transactions via the provider API, receiving and cryptographically verifying webhook callbacks using HMAC signatures, falling back to status polling when webhooks fail to deliver, processing full and partial refunds, and maintaining an immutable audit trail that satisfies both our internal compliance team and any external payment provider audits. We expect clean PSR-4 structure, proper exception handling with retry logic, and unit tests covering all critical paths. Documentation should be thorough enough that a mid-level developer can onboard and maintain the module independently.
Core requirements:
— PHP 7.4+ compatible module with PSR-4 autoloading
— Webhook endpoint with HMAC signature verification and replay attack protection
— Status polling fallback when webhook delivery fails
— Full and partial refund processing via provider API
— Admin transaction history view with search, filtering, and CSV export
— Unit tests with minimum 80% coverage of core transaction logic
Deliverables: standalone PHP module, OpenAPI 3.0 specification, integration guide with code examples.
The module must cover the complete payment lifecycle: initiating transactions via the provider API, receiving and cryptographically verifying webhook callbacks using HMAC signatures, falling back to status polling when webhooks fail to deliver, processing full and partial refunds, and maintaining an immutable audit trail that satisfies both our internal compliance team and any external payment provider audits. We expect clean PSR-4 structure, proper exception handling with retry logic, and unit tests covering all critical paths. Documentation should be thorough enough that a mid-level developer can onboard and maintain the module independently.
Core requirements:
— PHP 7.4+ compatible module with PSR-4 autoloading
— Webhook endpoint with HMAC signature verification and replay attack protection
— Status polling fallback when webhook delivery fails
— Full and partial refund processing via provider API
— Admin transaction history view with search, filtering, and CSV export
— Unit tests with minimum 80% coverage of core transaction logic
Deliverables: standalone PHP module, OpenAPI 3.0 specification, integration guide with code examples.
