PHP Developer - Outside IR35

Job Description

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PHP Developer - Payments Migration

Rate: £500 per day (Outside IR35)Duration: 6 monthsLocation: Mostly remote - once per month in London or Bristol

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.

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

Required Skills

• 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

Reasonable Adjustments:

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