So I'm new to both Joomla and Expression Engine, and want to know if I can use it like I'd like. I've already made a full site, and would like to integrate blogging into the site. The site is on CodeIgniter.
Is there a way that I could create a form template for submitting a post which would then save to my Joomla/CodeIgniter DB. Then, on a different page, use a different Joomla/CodeIgniter template to display the blog in the form I would like.
Note that this wouldn't necessarily be powered by EE or Joomla. From what I understand, and from all the examples I've seen, you have to make the html of the entire page inside of their templates.
At worst, if neither work, is there anything I can use to do this?
I would think EE would be the way to go since as of a few months ago, EE was 100% built on CodeIgnitor. I'm not sure from your question what you are trying to do - but in short, if you install/use EE to power your blog it is going to write to the EE database. That said, you can embed anything within an EE template (raw PHP or CI), including a form that would post to your existing site database.
There's some talk about this on the EE forums: http://expressionengine.com/forums/viewthread/74157/