Shopping Cart

Question

What should I take into consideration while building a Shopping Cart, for a eCommerce site (no metal work here =))?

Some clarification:
I'm only for suggestions for building the cart only, I can not use a prebuilt system or an external system (google, paypal)
And I have the processing done.

Answer 1

Do you need to build one at all? Most of this has been done for you in various shopping cart packages including google checkout, oscommerce, and others, but if you must take the plunge try to at least think about the following...

• Secure session for users
• Storing 'items' in the cart via the session / cookies
• Payment processing
  • what external systems do you interface with
  • what kinds of payments do you accept
  • what currencies do you accept
• Some kind of dispatching system for when a purchase occurs
  • If a purchase occurs, who is notified to mail out the items?
  • where is the purchase logged?
• Interaction with an inventory system of some sort
  • is the item in stock?
  • what to do when out of stock?
• Total / shipping calculations
  • how much do you charge shipping for different customers/destinations
  • where do you want to ship / where will you not ship

A shopping cart is far more complex a concept than it appears to be. The specific answer to these questions will depend on what kind of organization you are working for. Big company? Small startup? Family business? High volume vs low volume? Etc.

Answer 2

I'd be seriously considering if I'd need to build one at all.

There are plenty of cart packages around, both open source and commercial for pretty much every platform under the sun. Unless you have a very very specific need, I'd suggest evaluating what's already there first.