Code editors have built-in parsers that enable them to identify the parts of the code that are comments, PHP language functions, text strings, and a variety of other elements. Having these elements colored on the screen makes it much easier to read through code and to see that a function's name is not spelled correctly, or to quickly identify comments.
Another functionality that is crucial when developing plugins for WordPress is the ability to see line numbers in the editor. This function comes in handy, especially when PHP code errors come up, since the filename and line of code that was being processed at the time of the error are normally displayed. In most code editors, the developer can either scroll to the specific line or enter the line number in a quick Go To dialog box to jump to that line right away.