Adding custom functionality

I end up doing a lot of websites that are extremely basic except for that one niggling request.

For example they’ll want to have normal, editable pages on everything with nothing special…EXCEPT that one “contact me” form that suddenly needs to email to a user and contain a captcha and such.

Would SiteCake be able to still edit the textual content on the php page without interfering with the form functionality? Is this sort of thing even compatible with the way that SiteCake works?

In the current Sitecake 2.x version PHP code snippets are not supported. But, as this is one of the most frequent question/request, we’ll try to support it in the next release (at least, some simple cases).
For contact forms, I would suggest using a JavaScript/AJAX approach instead of a classic form submission.