Backend

In general, you can use anything as-is from the vendor library, or you can modify/add the functionality of existing classes by extending them in your project.

If you are familiar with the extending classes (class inheritance) in PHP language, you can skip this chapter. For the rest, here are some awesome descriptions of how it works:

• Interfaces
• Dependency Injection
• Abstract Classes
• Object Inheritance
• Namespaces
• Traits

Please get acquainted with these concepts before you continue because they will help you in the later chapters.