My B2B marketplace is built on a Custom PHP core (v5.2) and I’m upgrading new features on PHP 8.3. I need a developer who can bridge those two versions seamlessly while adding an end-to-end escrow and communication layer. Here is what I want produced: • Fully working escrow workflow Negotiation → Deposit → Proofing → Completion, with clear state management and error handling. • Payment gateway integration Paymob, Fawry and Xpay must process deposits, hold funds, and trigger releases inside the escrow logic. • Automatic Arabic PDF contract generator Every deal should output a professionally formatted, RTL Arabic contract that captures agreed terms and both parties’ signatures. • WhatsApp automation Using an API such as UltraMsg or Twilio, send “Smart Links” and status updates at each key step: Negotiation, Deposit, Proofing, Contract Signing, Payment, Approval (mock-up) and Delivery Confirmation. • Admin control panel Allow staff to view any transaction, pause or resume the workflow, and resolve disputes with the ability to refund or force-release funds. • Comprehensive technical documentation Explain in detail how the new PHP 8.3 module hooks into the existing 5.2 core, including models, endpoints, database migrations and webhook flow charts. Acceptance criteria – End-to-end escrow cycle completes without manual intervention. – Successful test transactions run through Paymob, Fawry and Xpay in sandbox and live modes. – Arabic contracts render correctly on browsers and mobile PDF viewers. – All WhatsApp messages reach test numbers with correct variables. – Admin actions instantly reflect on buyer/seller dashboards. – Documentation is clear enough for another developer to pick up the codebase. If you have solid B2B marketplace experience, deep PHP expertise and have connected regional gateways before, I’m ready to start right away.