My flights-and-hotels platform (custom-built in plain PHP) needs to start accepting payments through PesaPal right away. I already have the merchant account; what’s missing is a clean, secure gateway connection that lets travellers check out with Credit/Debit Cards, Mobile Money and Bank Transfers without ever leaving the site. Here’s what the assignment entails: • Build the full server-side integration against the PesaPal API (docs: https://developer.pesapal.com/), handling token generation, order submission, IPN/redirect callbacks and status verification. • Add the client-side checkout flow to our existing booking pages so that both flight and hotel reservations trigger a single, seamless payment experience. • Configure and verify sandbox, then migrate to live credentials. • Deliver concise setup notes plus any modified PHP files so I can replicate the work on staging and production. Acceptance criteria 1. A test booking for each product type reaches “Paid” status in the PesaPal merchant dashboard. 2. My system receives and records the final transaction reference and status. 3. No sensitive keys are left hard-coded; they load from env/config variables. I need the first working version within a few days, so please be comfortable diving straight into a custom codebase and turning around reliable results fast.