10/06/2026 updated
100 % available
Senior PHP Backend Developer - Laravel, Payment & LLM Integrations
Slovakia
Only remote
Specialist degree (5-year, Master's level).About me
PHP developer since 2013. Most of my work has been where money moves: payment gateways, checkouts and shop integrations. Recently I've also built LLM features in production. Based in Slovakia (EU), I work remotely in English and I'm available full-time.
AI AgentsLLME-CommercePython (Programming Language)LaravelPostgreSQLMySQLPayment GatewayPHP DevelopmentZend FrameworkFlaskBackend ProgrammingRestful ApiCode RefactoringWebhooks
Senior PHP backend developer with 13 years of experience (since 2013), specializing in e-commerce, payment integrations and LLM-powered features.
Payment integrations:
- Payment gateways and aggregators: Klarna / Sofort, iDEAL, Mollie, Paysafecard, TargetPay, Paygol, Clearhaus, CorvusPay, FastSpring, Micropayment
- Development of a payment aggregator on Yii2
- Checkout modules, payment callbacks / webhooks, order and stock logic
Backend development:
- PHP, Laravel, Zend Framework 3, Yii2, CodeIgniter, Doctrine ORM
- Python, Flask
- REST API design and third-party API integrations, data synchronization between systems
- PostgreSQL (incl. JSONB), MySQL
E-commerce:
- OpenCart / ocStore — custom modules, checkout, admin panel extensions, CRM integrations
- 1C accounting system integration
AI / LLM integrations:
- LLM API integration (OpenAI-compatible APIs, multi-provider routing via LiteLLM)
- Structured outputs, RAG, prompt engineering, token cost optimization
- AI-generated product content for e-shops
DevOps & tools:
- Docker, Docker Compose, Git, Bitbucket, Linux (Ubuntu, CentOS)
Frontend (supporting): JavaScript, jQuery, HTML, CSS, Tailwind CSS, Bootstrap
Industries: e-commerce, payments / fintech, SaaS, online platforms.
Experience
Professional experience10+ years
Freelancer since2017
Languages
EnglishGoodRussianNative speakerSlovakBasic knowledge
Project history
Multi-tenant task management and time-tracking SaaS with Kanban boards and invoicing for small businesses. Slovak localisation, GDPR-compliant.
Backend development of a platform integrated with several external platforms: profile and media synchronisation on a unified JSONB data model, integration with an AI service (typed Value Objects for responses), reconciliation tooling that detects data discrepancies between external platforms and the internal system.
Built an AI service (Python) that generates messages and replies in user conversations: multi-provider LLM routing via LiteLLM, output validation and post-processing pipeline, token-cost optimisation for multilingual content.
Integrated online shops with 10 payment providers and aggregators: Klarna/Sofort, iDEAL, Mollie, Paysafecard, TargetPay, Paygol, Clearhaus, CorvusPay, FastSpring, Micropayment. Took part in developing a payment aggregator on Yii2 (2021). Built an online shop from scratch, OpenCart 3 checkout module and admin extensions, statistics feature on CodeIgniter. Clients included SOLYS s.r.o., Skylab s.r.o., Adept Media Group s.r.o. and Attorneum.