Because the typical purpose of launching an online store is to trade goods for monetary payment, a key part of any ecommerce application is the actual code to process the payment information given to us by the customer. Unless you are a large corporation or service provider with your own processing facilities or servers, chances are you are going to have to work with some sort of external payment processing provider.
Fortunately, there are many such providers. They are either well supported by PHP, or do not require extra code in the language engine and integrate seamlessly into your application.
In general, at least the following will have to be completed:
Searching on the Internet for "credit card processing PHP" will turn up a large number of options, but some other common places to look for further information are as follows: