Paypal API integration

I need a paypal api script that I can drop into my html. The visitor must remain on my site throughout the purchase. The first user interfaec is a credit card form that will charge a fixed fee. The second user interface is a credit card form that will charge a fixed subscription fee. Upon the successful completion of these transactions the php script will be required to populate my MySql database with as much information as returned by paypal. Of prime importance, the user must remain on my domain at all times. I am not using any ecommerce platform or framework, so the ideal candidate should have experience with custom-built websites. Other required skills include:
- Proficiency in PHP programming language
- Knowledge of Paypal API
- Experience with payment gateway integration
- Attention to detail and ability to troubleshoot issues
Please provide examples of previous Paypal API integrations you have completed.