Yannick Lefebvre's is structured around practical "recipes" that guide you through extending WordPress functionality. A standout feature you can implement from its teachings is a Custom Administration Page with a functional Settings API integration . Feature: Custom Plugin Settings Dashboard
From an official Packt PDF, code blocks are clean. If yours isn’t, you likely have an illegal copy.
Then check /wp-content/debug.log to see PHP errors as you tweak the code.
Transforming WordPress from a blog engine into a full-fledged Content Management System (CMS).