WordPress offers one of the most flexible plugin architectures, alongside other similar frameworks such as Joomla and Drupal. The existence of over 35,000 plugins in the WordPress plugin directory proves the vital role of plugins. In typical websites, we create simple plugins to tweak the theme's functionalities or application-specific tasks. The complexity of web applications forces us to modularize the functionalities to enhance their maintainability. Most applications developer will be familiar with the concept of the open-closed principle.
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The open-closed principle states that the design and writing of the code should be done in a way that new functionality should be added with minimum changes in the existing code. The design of the code should be done in a way to allow the addition of new functionalities as new classes, keeping as much of the existing code unchanged as possible. You can find more information at http://www.oodesign.com/open...