Magento module configuration file reference

The most important file in custom modules development is config.xml. With the help of this file you can override models, blocks, helpers; define custom controllers, module version, table names, cache types; load your layout files, etc. About all of these you will learn from the article.

Module bootstrap and configuration files load order

The module configuration file will not be loaded without a bootstrap file. The bootstrap files of modules are placed in app/etc/modules. Usually all of them are named the same as the module. But you can define more than one module in file, such an example is placed in Mage_All.xml file. The basic structure of a boostrap file:

<?xml version="1.0"?>
<config>
    <modules>
          <Namespace_Modulename>
                 <codePool>local</codePool> <!-- local or core or community -->
                 <active>true</active> <!-- true or false -->
                 <depends>
                       <Namespace_Modulename1 />
                       <Namespace_Modulename2 />
                       <Namespace_Modulename3 />
                 </depends>
          </Namespace_Modulename>
    </modules>
</config>

The description of each node you can find in the following list:
Click on the node name to see its description

modules
All the modules are placed under this node, the node content is merged from all the bootstrap files into the one structure. If you have added new module boostrap file, but it will not show up. Just refresh the cache, because the merged structure is cached by default.
- [Namespace_Modulename]
  The name of this node defines the module namespace path. Of course you can use structure with more than one underline character, but the best practice to camelize module names that contain more than one word. For example, EcomDev_ProductPageShipping and EcomDev_Product_Page_Shipping is allowed, but the first one is preferable, because each underline character equals to slash in directory structure.
  - codePool
    This node defines the code pool of the module. Possible values are core, community and local. These values are the names of the folders in app/code directory. All the modules from Magento Inc. core team usually are placed in core. Community should contain Magento Connect extensions . Local usually is used to perform some local modifications.
    This node is required.
  - active
    Module activity indicator, if you do not specify the node value, it will be disabled by default. Possible values are true and false.
  - depends
    This node specifies dependencies and load order of the module. If your module requires another one or need to be loaded only after it, you should just mention it as a child node. The system will rise an error if the required module does not exist or is not activated.

You may have already noticed that if you place some configuration nodes like in module config.xml file, it will not affect on the configuration. The module bootstrap file is created only to define module initialization values, it is not the actual configuration file.

Module main configuration file

Each Magento module has its main configuration file (etc/config.xml), that contains definitions of models & blocks namespaces, controller routes, database resources, layout file paths, etc.
Take a look at the following example of a simple configuration file:

<?xml version="1.0" ?>
<config>
    <modules>
        <Namespace_Modulename>
            <version>1.1.1</version> <!-- the version of module resources -->
        </Namespace_Modulename>
    </modules>
    <global> <!-- global scope, also known as the default configuration area -->
         <models> <!-- definitions of the module models namespaces -->
             <namespace_modulename>
                 <class>Namespace_Modulename_Model</class>
                 <!-- definition of model resource model -->
                 <resourceModel>namespace_modulename_resource</resourceModel>
             </namespace_modulename>
             <namespace_modulename_resource>
                 <class>Namespace_Modulename_Model_Resource</class>
             </namespace_modulename_resource>
         </models>
         <blocks> <!-- a defintion of the module blocks namespace -->
             <namespace_modulename>
                 <class>Namespace_Modulename_Block</class>
             </namespace_modulename>
         </blocks>
         <helpers> <!-- a definition of the module helpers namespace -->
             <namespace_modulename>
                 <class>Namespace_Modulename_Helper</class>
             </namaspace_modulename>
         </helpers>
         <resources> <!-- a resource setup files path defintion -->
             <namespace_modulename_setup>
                 <setup>
                     <module>Namespace_Modulename</module>
                     <class>Namespace_Modulename_Model_Resource_Setup</class>
                 </setup>
             </namespace_modulename_setup>
         </resources>
         <events>
             <event_name>
                 <observers>
                      <unique_observer_name>
                          <!-- or you can specify class node, it is the same as model -->
                          <model>namespace_modulename/observer</model>
                          <method>listenerMethodName</method>
                      </unique_observer_name>
                 </observers>
             </event_name>
         </events>
    </global>
    <frontend>
         <layout> <!-- definition of layout update for frontend area -->
             <updates>
                 <unique_update_name>
                     <file>namespace/modulename.xml</file>
                 </unique_update_name>
             </updates>
         </layout>
    </frontend>
</config>

This file defines the module with own models, blocks, helpers, a resource setup, a frontend layout update and one event observer in the global scope. I hope it will not confuse you and you are already familiar with such words those are used here.

The description of nodes those are the most used during custom modules development. I have summarized them by categories and areas where they are used.