I used both CF and PHP for a similar purpose: execute database queries in the backend from the front flash movie. These flash clips were similar to your situation, more or less autonomous, not very integrated into the website.
I found that with CF you can do more than with PHP. Database operations are much easier to perform in CF than PHP, and more on that. However, if your SQL skills are not too shabby, this is not a big problem.
IMHO, your needs are better suited to PHP because it is free and you can get WAMP or LAMP easily configured as your sandbox. If you just need a sandbox for CF, you either have to βpayβ the sticker price * for the official Adobe software, or get significantly lower simulations like Railo Server .
Note that for me I was able to perform database operations on the server using WAMP / LAMP and Adobe CF, but not Railo, so this greatly limits your sandbox experiments with CF. That was 9 months ago, so you might want to check to see if Rail has improved with it.
As far as libraries are concerned, there are much more options for PHP than for CFs, due to the much larger developer community. Data from Google:
PHP: 15 million views
CF: 0.5 million views
In short: go with PHP.
NTN
Edit:
As Al mentioned, CF developer release is free.
source share