Create folder structure and configuration files

Before the first lines of code can be written, it is necessary to create the basic infrastructure of the extension. To allow TYPO3 to load the extension, some default configuration files must be created. Let’s start by creating a folder store_inventory in the folder typo3conf/ext/ - the folder name store_inventory corresponds to the unique identifier of our extension (also known as “extension key”).

Tip

The extension key may only contain small letters and underscores (lower_underscore).

Hint

Extensions can be stored at different places in TYPO3. Locally installed extensions are the rule. These are in the folder typo3conf/ext/. Global extensions are in the folder typo3/ext/. System extensions are in the folder typo3/sysext/. Extbase or Fluid are examples of system extensions.

The folder structure

Inside of the folder store_inventory the sub folders Classes and Resources must be created. The folder Classes must contain all of the PHP class files. In the folder Resources two directories named Private and Public must be created. The folder Resources/Private/ will contain subfolders like Templates, Layouts, Partials and Language. These files are not accessible via the web browser, they are mostly used via PHP. The folder Resources/Public/ contains subfolders like Icons, Css, Js. These files can be accessed through the web browser.

Within the folder Classes the subfolders Controller and Domain must be created. In this example, the folder Controller contains only one class that will control the entire process of listing creation later. The folder Classes/Domain/ contains the two folders Model and Repository. Resulting from all this, the folder structure within the extension folder store_inventory should look as in image 4-1.

Figure 4-1: The default directory structure with the important files for the extension manager

Configuration file ext_emconf.php

The configuration file named ext_emconf.php is required by TYPO3 in legacy installations not based on Composer. It is recommended to keep this file in all extensions that are being published.

The file is located in the extension’s top-level folder (store_inventory/). You can copy and adapt this file from an existing extension.

The file ext_emconf.php contains the meta-information for the extension like title, description, status, name of the author, and more. It is not special in any way and does not differ from the one of any other extension. Find a complete reference in chapter Declaration file (ext_emconf.php) of the Core Api Reference manual.

<?php

$EM_CONF[$_EXTKEY] = [
    'title' => 'Store Inventory',
    'description' => 'This TYPO3 extension is an example in the Extbase Fluid Book. See external documentation',
    'category' => 'plugin',
    'author' => 'TYPO3 Documentation Team',
    'author_company' => 'TYPO3',
    'author_email' => 'documentation@typo3.org',
    'state' => 'alpha',
    'clearCacheOnLoad' => true,
    'version' => '11.0.0',
    'constraints' => [
        'depends' => [
            'typo3' => '11.0.0-11.99.99',
        ]
    ],
    'autoload' => [
        'psr-4' => [
            'T3docs\\StoreInventory\\' => 'Classes'
        ]
    ],
];

In previous versions of TYPO3, the extension icon was named ext_icon.gif. Starting with TYPO3 8, you can choose between PNG or SVG format. It is recommended to call the file Extension.png or Extension.svg and store it in the directory Resources/Public/Icons/. The icon will be displayed in the extension manager and in the TYPO3 extension repository (TER).

Configuration file composer.json

Next to the ext_emconf.php you should add a composer.json file. It enables the extension to be loaded in all Composer installations of TYPO3.

{
   "name": "t3docs/store-inventory",
   "type": "typo3-cms-extension",
   "description": "This TYPO3 extension is an example in the Extbase Fluid Book. See external documentation",
   "license": [
      "GPL-2.0+"
   ],
   "authors": [
      {
         "name": "TYPO3 Documentation Team",
         "role": "Developer"
      }
   ],
   "autoload": {
      "psr-4": {
         "T3docs\\StoreInventory\\": "Classes/"
      }
   },
   "require": {
      "typo3/cms-core": "^11.0.0"
   },
   "replace": {
      "typo3-ter/store_inventory": "self.version"
   },
   "extra": {
      "typo3/cms": {
         "extension-key": "store_inventory"
      }
   }
}

After the basic structure has been created, the extension can now be activated in the extension manager. But first the domain must be developed.