There is another option available to you that gives you a quick way to continue creating websites in exactly the same way as your are used to, you then have no need to learn and maintain PHP code or get to grips with MySQL databases, so allows you to stay focused on designing great websites instead of becoming a software developer. You could use a hosted shopping cart add-in to do this which means all the development and store software management is taken care for you by the hosted shopping cart add-in service.
All you would need to do is copy and paste the hosted shopping cart add-in text/script in to your web pages to give you Add to Cart, Buy Now, Checkout buttons and other add-ins like Total Cost of Cart, Total Number of Items In Cart etc.
It is then a simple step to connect your website to your chosen payment processor, like PayPal, who then handle the credit card payment at the final checkout stage.
A good hosted shopping cart add-in allows you to create a professional looking online store embedded in to your website and will give the merchant lots of great features, like stock quantity control for instance, or automatic storage and delivery of digital downloads.