Senior PHP Developer — Custom Fintech Lending Platform (UK, Part-Time)

We're building Credicorp — a custom PHP fintech platform for a UK-based exempt business lender (RAO 60C/60H). The stack is bespoke MVC PHP (no framework), MySQL, REST APIs, and vanilla JS. No WordPress, no Laravel — pure custom code. We're looking for a senior PHP developer to work alongside our AI-assisted build pipeline, reviewing output, filling gaps, fixing bugs, and extending features. The codebase covers: - Lending decisioning engine (AI-driven, behavioural scoring, credit risk) - Customer portal (self-serve arrangements, payment flows, document upload) - Staff/MRS dashboard (pipeline management, collections, disbursement) - Marketing site (PHP + static) - Shared service layer (CSRF, session, auth, API clients, webhooks) What we need: - Senior PHP (5+ years) — clean, secure, well-structured custom PHP - MySQL — schema design, query optimisation, migrations - REST API design and integration (Stripe, Open Banking, identity verification) - Security-first mindset — CSRF, SQLi, XSS, input validation - Ability to read and extend an unfamiliar codebase quickly - UK timezone preferred (GMT/BST) — async is fine, occasional overlap helpful This is part-time and ongoing — roughly 20-40 hours/month to start, with the potential to increase. You'll have GitHub access, clear tickets, and direct communication. No micromanagement. Rate: $15-25/hr. Please include examples of custom PHP work (not WordPress/framework sites) in your application.