The power of Drupal can only be leveraged best if you learn how to write your own custom modules. If you know a bit of PHP and aren’t intimidated by functions, elements, arrays and the like, this is the best place to start. Drupal.org Community Docs. This tutorial will take you through the ins and outs of writing a basic but very functional Drupal module. This tutorial will, in great detail, explain all the steps needed to create a module that will allow you to show a configurable number of posts in a block, create a configuration menu option for the module and include a Help page.
I’ve looked at many online tutorials on how to write basic modules and this one is the best. It has the most thorough explanations and is rigorous in its adherence to Drupal commenting standards, coding standards and naming conventions. As well as the Drupal specific functions that make developing for Drupal easier. If you want to learn Drupal PHP development, this is the place to start.