If your a small ecom provider doing a custom LAMP ECOM build and just getting started would agree with the other comments. You would not want to store any card data at all.
That said PayPal has a good ecom system as an example . I have used this one -https://www.paypal.com/webapps/mpp/merchant. It works well and you do not store any credit card data onsite. It allows you to do your own custom basket and shopping carts and then upon checkout the customer is redirected to paypal web services for credit card clearing.
(There are several others) Make sure on your ecom site- you have a tab about web security and talk how your are PCI compliant by using a service like this.
You will be storing some data in a DB within the LAMP stack. Customer information, Mailing address, Phone numbers. All of that data that is resting in the SQL DB should be encrypted and be behind stand DMZ architecture with hardened servers.
Also - you consider doing a simple web application pen test prior to launching the service.
If your site starts making money - consider spending some money on a continuous scan service like from Mcafee. http://www.sitelock.com/products.php . The pitch you will hear is that with the Mcafee scan service stamp on your site - consumers will feel better about your site security.