Different types, but strong overlap

We looked at the different types of CMSs, from general-purpose to photo galleries. Each had its own core feature set, but all the CMSs have a strong overlap of functionality. They all essentially allow you to add and manage some type of content—text, images, and files. The way content displays to the end user may be different, but a lot of internals are the same. Here are some of the features you will see in many CMSs:

As we evaluate each type of CMS later in the book, you will experience the striking similarity in the way content is managed. This is good news actually—you can easily apply lessons you have learned from one CMS to another.

One more striking similarity you may notice is that most open source CMSs are written in PHP. Let's quickly review CMS technologies to understand this phenomenon.