PHP Payment Gateway Integration

I need a developer who can connect my existing PHP site to a reliable payment gateway. The goal is to give customers a smooth, secure checkout experience from start to finish. I am currently leaning toward well-known services such as PayPal, Stripe, or Square, but I am open to your recommendation if another platform would suit the codebase better. You will be working with a live production environment, so clean, well-documented code and clear hand-off notes are essential. If you have prior experience handling tokenization, secure storage of credentials, and sandbox/live environment switching in PHP, that will help us move quickly. Once the integration is complete I’ll run a few test transactions; as long as those settle correctly and the confirmation callbacks reach my application, I’ll consider the hand-off successful. Budget: USD 10–30