Add CMS functionality to your existing website it just one line of code.

Now use an admin interface to decide what content type/plugin to use.
Will it be a blog, html, wiki or something else?

Check out the list of plugins for all the available features.

Content CMS aims to provide just CMS functionality. Tell Content CMS to manage a section of content and then head to the admin section to decide on the content you want.

The extendible design of Content CMS allow you to grow the CMS as you require. By allowing you to add functionality later, you can get to grips with the functionality you require now.

If you want a connection to a database then use whichever method you want, mysql_connect, mysqli, don't even use mysql. Content CMS is about innovation not limitations.

I didn't originally set out to start a CMS but what I wanted was a CMS that I could add to an existing website. I found a couple of them out there (Perch and Couch CMS)

The downside is that they are commercially supported products, to ensure they are supportable there are restrictions, APIs and limits. Ask yourself, do you want to learn a CMS API? or do you want to learn PHP?