WordPress allows adding extra content to your post or page contents with custom fields. This is useful if the the content is simple text value. You can still use it for other types of data such as image and radio buttons. But it’d be nice if there’s a nice user interface to simplify the process, to allow different types of input and to validate the input.
There are quite a number of plugins to enhance the use of custom fields. One of the most popular plugins is Advanced Custom Fields. I have used it on a few projects, until I needed repeating groups for a set of fields. Yes, ACF does provide such functionality but it’s not free.
Then I discovered Simple Fields. It’s quite powerful and satisfies all my requirements. You can customize for different data types and it allows repeating groups! Documentation is quite complete too. Sadly this plugin is not actively developed anymore.
I still find this plugin quite useful and haven’t had any problems with it (as of WordPress V4.4.2).
However, since it’s no longer actively developed, I’ll have to start looking at other plugins that provides the same functionality since it may not work with later versions of WordPress. If you have any recommendations please leave a comment.