PHP Developer - Outside IR35

We are looking for an experienced PHP contractor to own and deliver the PHP-side of the migration, ensuring existing payment journeys are updated to integrate with the new external payment component, while safely decommissioning legacy in-application payment logic.

This role sits at the intersection of legacy PHP, payments, and service integration, and requires a strong focus on security, reliability, and seamless user experience.

Responsibilities

• Modify existing PHP payment journeys to redirect or hand off to a new external payment component
• Implement secure redirect and callback handling between the PHP application and the AWS-hosted Java microservice
• Collaborate with the Java/AWS team to define and agree:

• Integration contracts
• Redirect URLs
• Tokens and callback payloads

• Ensure appropriate audit logging, error handling, and traceability throughout the migration
• Support regression testing and extend existing test coverage
• Contribute to Codeception and Jest test suites as required

• Strong commercial experience with PHP 7.x, ideally within large legacy or monolithic codebases
• Hands-on experience with payment integrations, such as Stripe
• Strong understanding of 3DS flows and PCI-DSS considerations
• Proven experience migrating functionality out of a monolith into external services
• Good understanding of HTTP integrations, service layers, and API contracts
• Experience implementing secure redirect patterns, such as:

• OAuth-style flows
• Signed URLs
• HMAC tokens

I am currently working with a leading financial services company to undertake a critical migration of payment functionality from a legacy on-premise PHP monolith into a new AWS-hosted Java microservice owned by a separate engineering team.