Code pools

The folder code is a placeholder for what is called a codePool in Magento. Usually, there are three code pools in Magento, that is, three subfolders: community, core, and local.

The folder local is sometimes missing from the downloaded installation archive, as it is empty by default.

Let's take a deeper look at the community codePool for the default Magento installation as shown in the following diagram:

community/
└── Phoenix
    └── Moneybookers
        ├── Block
        │   ├── Form.php
        │   ├── ...
        │   └── Redirect.php
        ├── Helper
        │   └── Data.php
        ├── Model
        │   ├── Abstract.php
        │   ├── ...
        │   └── Wlt.php
        ├── controllers
        │   ├── MoneybookersController.php
        │   └── ProcessingController.php
        ├── etc
        │   ├── config.xml
        │   └── system.xml
        └── sql
            └── moneybookers_setup
                ├── install-1.6.0.0.php
                └── mysql4-upgrade-1.2-1.2.0.1.php

Here, the Phoenix folder is what is called the vendor namespace, and it usually matches your company identifier or something else unique to you. Within the Phoenix folder there is a Moneybookers subfolder that stands for your actual extension name.

To summarize, the formula for your extension code location should be something like app/code/community/YourNamespace/YourModuleName/ or app/code/local/YourNamespace/YourModuleName/.

There is a simple rule as to whether to choose community or local codePool:

For example, let's imagine that our company name is Foggyline and the extension we are building is called Happy Hour . As we wish to share our extension with the community, we can put it into a folder such as app/code/community/Foggyline/HappyHour/.

All the Magento core code is also divided into extensions, and is located under the app/code/core/Mage folder. You should never place any of your code or edit any of the existing code under the app/code/core folder.

Let us get back to our example from the previous listing, the Moneybookers extension. We can see that it has several subfolders within it:

With that said, we will temporarily conclude our trip to the app/code folder structure and move on to the app/etc/modules folder.

This folder is basically a starting point for every Magento extension. The following listing shows the default content of the app/etc/modules folder for the default Magento installation, which is a collection of XML files:

For example, if we were to create our Foggyline/Happy Hour extension, we would need to create a file app/etc/modules/Foggyline_HappyHour.xml as we will show later on.

Next, we move onto the app/local folder. This is where the translation files reside. If you were building an extension that would support multiple languages, for example English and German, you might want to create the following files:

The exact filename in this case does not have to be Foggyline_HappyHour.csv; this is something that is set by you within the extension configuration.