I have done a considerable amount of work in PHP, both on original scripts and the customization of popular open source web applications. Although I prefer to work in ASP.NET, there just aren't enough open source web applications available using that technology. There are a variety of PHP web application frameworks so most of my PHP work has required me to explore and understand someone else's code and methodology. Therefore I have developed the skills needed to take up where a previous developer has left off.
Drupal actually rarely requires any PHP coding. There are modules for everything you could need. Customizing a Drupal site often involves more CSS, web design, and back end administration than writing code. However, it is sometimes necessary to add a little PHP code to get the right file path for images in a tricky web design or page layout. On rare occasions you may also need to change something manually in the database to fix a problem.
I have never built a site from scratch using CodeIgniter but I'm currently maintaining a web application that uses this web application framework. This requires some basic understanding of the model–view–controller (MVC) software architectural pattern.
I have some experience with WordPress since my blog is using WordPress. I have troubleshooted various errors that sometimes appear after updating WordPress or a plugin. My web site is running on a shared Windows server so the server environment is not optimized for running WordPress. I have also worked on a few projects that mostly required tweaking the design of a WordPress content management site.