Core Php back end work customisation

I am looking for a skilled Php developer to customize the payment gateway integration for my project's back end. Specifically, I would like to integrate a payment gateway that will allow users to easily make payments for the services offered on my website.

Skills and experience needed:
- Strong knowledge of Php and back end development
- Experience in payment gateway integration
- Familiarity with popular payment gateway providers such as PayPal, Stripe, etc.

Authentication method:
- Email and password

Timeline:
- Flexible (more than 3 weeks)