About E-commerce web site in php

Hello Every one,

I got new project that is based on E-commerce (shopping cart).
Now if i talk about security in this web site than on what security should concentrate.

Please tell me the security features that should be in this web site.

thanks.

http://www.flashfiredesigns.com/resources/website_security/securing_your_php_application_from_hackers.php

http://www.owasp.org/index.php/Main_Page