"Patch" core files osCommerce (old) or upgrade?

Hey guys, I have a client who wants me to update a site, which is running on oscommerce v 1.18.

What he wants me to do is make the HTML w3c compliant. There appear to be lots of tables being incorrectly used as well as other violations of today's standards, and i'd like to fix this, but the view layer has a l开发者_StackOverflow中文版ot of business logic in it, and it's very mixed together.

Should I just try to get the client to upgrade the system? Anyone else deal with a similar situation? Either way, it seems like a fairly big undertaking. As always, thanks for your time and opinions!

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Basically I would lay out the options, and outline the security concerns for the client. After all you are probably getting paid per hour, so you shouldn't worry about the work effort involved as long as you are compensated.

With that said, upgrade is always the best route compared to hacking it out and trying to fix it even tho you are in a hole (security / update / patch wise).

Just food for thought.

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There are no conceivable circumstances under which it would be ok to keep using osCommerce.

Instead of trying to update to a newer version, investigate and test if you can utilize any (semi-) automated migration tool. http://www.magentocommerce.com/magento-connect/Magento+Core/extension/114/os-commerce-import
Spending less time for more benefits is more likely to please the client.

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Changing core file of an application can never be a good thing (I don't say it can't be done but...), you should take care as maybe someone else will take back the project and try to upgrade the application and break all your custom made code.
Go for it if it is your last resort.

If you just need to update html markup, well, it should be feasible, however as a professional, you should really advise your client and tell him what you think is good for him.

Maybe you should advise him to switch to a better e-commerce application, there are plenty now which are far better than OsCommerce.

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Editing the core files is almost always a bad idea. If one day you finally want to do the upgrade, you won't able to be sure that all the data are managed the way they should be, etc ...

And I don't even talk about security issues, when touching core's files.