ecommerce related question

Firstly, not really a php question, but generic web stuff, but I feel it's still better answered here. Recently a friend came to me asking to create an ecommerce website. In the past my php work has been primarily a hobby, and as such haven't really taken much interest or effort into security aspects of it. Given the nature of the project, I realise security is a must. My question is: what recommended reading for security or ecommerce can any of you suggest? -- Thanks, Travis Moore trav.m@live.com OR trabus2005@gmail.com