Merchant account for php website

I’m on the learning path for php, mysql etc and am setting up a website.
I am at a stage where I will be wanting to hook the site into some kind of merchant account processing ie: Paypal and accepting credit cards.
I’m hoping that folk have had experience of this and can point me in the right direction as to who offers the best and most reliable service and how easy/difficult it is to hook into a php website design.
I’m looking for an account that would take on all the security respopnsibility and protocols

hope this all makes sense and I hope I’ve put this in the right place