Extending an existing system is always an interesting and challenging job. You have to care about the existing code base and structure and extend it in such a way that the design does not collapse after merging those extensions. This chapter discusses extending WordPress in detail by developing plug-ins and widgets. This chapter also shows us how to design widgets with multiple-instance support.
Extending WordPress is like a never-ending adventure. These days many services are published with an extremely simple set of APIs and we can integrate many of those into our WordPress blog. So reading this chapter will help you start this amazing journey by yourself.