First orientation

The blog example is an example extension, which mainly focuses on showing the process of extension development and shows the possibilities of an extension based on Extbase. This extension is a common blog, which can be administrated either through the TYPO3 backend or in the frontend. The blog example includes the standard features, which you will know from other blogs: A blog consists of several posts, and the readers of the blog can comment on the posts. The author of a post can add one or more tags to his post. Figure 3-1 shows an overview of the blog example’s domain and the relation among the domain terms. The asterisk (* or 0..*) means “any amount”, 1 has to be translated with “exactly one”. So exactly one administrator can administrate any amount of blogs. The diamond symbol can be translated with “has”, so: “One post has any amount of comments”.

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Figure 3-1: Domain of the blog example

The complete source code can be found in a folder with the same name as the extension key. In our case, the folder is called blog_example. Usually, the folder is located in the path typo3conf/ext/ in your TYPO3 installation.

In the top level of this folder there are the subfolders Classes, Resources and Configuration (see figure 3-2). There also are some files that TYPO3 requires to include the extension. Those files have the prefix ext_. All other configuration files needed by TYPO3 are located in the subfolder Configuration or in one of its subfolders.

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Figure 3-2: folder structure of the example extension

The core of the extension is located in the folder Classes. There you will all files in which classes or interfaces are defined.

Note

If you are not familiar with the terms “classes” and “interfaces”, you should look into Object-oriented programming with PHP 7 .

The folder Resources contains media and text files included at runtime, but no PHP classes or interfaces. Those are icons, language packages, HTML templates, and external libraries or scripts. These resources are structured into a public (Public) and a private (Private) directory. The folder Public holds files allowed to be called directly by the client - in normal cases, the web browser. Files processed by a PHP class before they get delivered to the browser, are located in the folder Private.