Create a new module in magento

When you need to add new functionality or want to edit existing magento class in both case you should create a new module. Suppose, you want to add “User Credit” system then you need to create a new UserCredit module in magento. And if you want to edit/update customer functionality  then you should follow magento override rules. To override existing Customer module you should create another new customer  module name M4U_Customer in local pool. In this case you need to use magento rewrite rules. When you go to add or edit something in magento,  each time you can be done as separate module or few methods can be combined in same module if they share functionality or could be used together.

Let’s create a module :

Module Declaration:
Create app/etc/modules/M4U_NewModule.xml and write below code

<?xml version="1.0"?>
<config>
         <modules>
<!-- declare CompanyName_NewModule module -->
           <M4U_NewModule>
<!-- this is an active module -->
                  <active>true</active>
<!-- this module will be located in app/code/local code pool -->
                  <codePool>local</codePool>
<!-- specify dependencies for correct module loading order -->
                  <depends>
                             <Mage_ExistingModule />
                  </depends>
<!-- declare module's version information for database updates -->
                  <version>0.1.0</version>
           </M4U_NewModule>
	</modules>
</config>

Here is example of create new M4U_customer module to override existing Mage_Customer module and M4U_Credit module to create new credit module.

<config>
    <modules>
        <M4U_Customer>
           <active>true</active>
           <codePool>local</codePool>
        </M4U_Customer>
        <M4U_Credit>
           <active>true</active>
           <codePool>local</codePool>
        </M4U_Credit>
    </modules>
</config>

Our new module will be called NewModule.

Replace all instances of ‘NewModule’ with name of your module and ‘newmodule’ with simplified code, that contains only alphanumeric characters and underscore.

To make this tutorial most concise, it’s implied that mentioned folders will be created when needed.

Module Configuration:

Create Model, Helper, coltrollers, Block, sql and etc folder under  app/code/local/M4U/NewModule/ and configure app/code/local/M4U/NewModule/etc/config.xml like below:

<?xml version="1.0"?>
   <config>
       <modules>
           <M4U_NewModule>
                 <version>0.1.0</version>
           </M4U_NewModule>
       </modules>

<!-- define Front end controller and template  -->
       <frontend>
<!-- define Front end controller  -->
           <routers>
               <newmodule>
                   <use>standard</use>
                   <args>
                          <module>M4U_NewModule</module>
                          <frontName>newmodule</frontName>
                   </args>
               </newmodule>
           </routers>
<!-- define Front end template xml -->
           <layout>
               <updates>
                    <newmodule>
                         <file>newmodule.xml</file>
                    </newmodule>
                </updates>
              </layout>
           </frontend>   

<!-- define blocks, models, helpers in global area -->
            <global>
               <models>
                  <newmodule>
                         <class>M4U_NewModule_Model</class>
                  </newmodule>
               </models>
               <blocks>
                  <newmodule>
                          <class>M4U_NewModule_Block</class>
                  </newmodule>
               </blocks>
               <helpers>
                  <newmodule>
                          <class>M4U_NewModule_Helper</class>
                  </newmodule>
               </helpers>

<!-- declare resource setup for new module -->
               <resources>
                    <newmodule_setup>
<!-- specify that this resource is a setup resource and used for upgrades -->
                       <setup>
<!-- which module to look for install/upgrade files in -->
                           <module>M4U_NewModule</module>
                       </setup>
<!-- specify database connection for this resource -->
                       <connection>
<!-- do not create new connection, use predefined core setup connection -->
                           <use>core_setup</use>
                       </connection>
                    </newmodule_setup>
                    <newmodule_write>
                         <connection>
                              <use>core_write</use>
                         </connection>
                    </newmodule_write>
                    <newmodule_read>
                         <connection>
                               <use>core_read</use>
                         </connection>
                    </newmodule_read>
                </resources>
           </global>
      </config>

Adapter Class:
To obtain module functionality you can write necessary method in various classes as magento convention.
1. Create necessary model class in app/code/local/M4U/NewModule/Model/
2. Create Block in app/code/local/M4U/NewModule/Block/
3. Create Helper in app/code/local/M4U/NewModule/Helper/
4. Place necessary updated database sql file in app/code/local/M4U/NewModule/sql/

Frontend Template Define:

1. Define page layout in app/design/frontend/M4U/default/layout/NewModule.xml

<?xml version="1.0"?>
   <layout version="0.1.0">
     <newmodule_index_usercredit>
        <reference name="root">
            <action method="setTemplate"><template>page/1column.phtml</template></action>
        </reference>
        <update handle="customer_account"/>
        <reference name="content">
            <block type="newmodule/blockClassName" name="usercredit" template="newmodule/usercredit.phtml"/>
        </reference>
     </newmodule_index_usercredit>
</layout>

2. Create template file app/design/frontend/M4U/default/template/newmodule/usercredit.phtml

Troubleshooting

• Dont put your module in /Mage. It belongs in app/code/community/ or app/code/local/
• Make sure your module’s first letter is capitlized. newmodule apparently will not work, it must start with a capital letter Newmodule.
• If your module is not showing in configuration>advanced then check your config.xml
• Make sure you clear the cache.

In this post i described general module customization theory of Magento. For more clarification you can see next post  “write HelloWord module” in this blog.

Magento Helper override rules

Sometimes Magento uses helper class to retrieve some of the help info such url, name, group etc. So you have to override helper class when you want to change any url or something else. Helper class override  is similar to block and model override. Here i described details about helper override with example.  Here i show how to override helper class Mage_Customer_Helper_Data.

1. At first create new module to process override work and write below code in app/etc/modules/M4U_Customer.xml

<?xml version="1.0"?>
       <config>
             <modules>
                  <M4U_Customer>
                       <active>true</active>
                       <codePool>local</codePool>
                  </M4U_Customer>
            </modules>
     </config>

2. Do configuration in app/code/local/M4U/Customer/etc/config.xml

<?xml version="1.0"?>
    <config>
        <modules>
            <M4U_Customer>
                <version>0.1.0</version>
            </M4U_Customer>
        </modules>

        <global>
           <helpers>
              <customer>
                  <rewrite>
                      <data>M4U_Customer_Model_Customer</data>
                 </rewrite>
              </customer>
           </helpers>
        </global>
  </config>

3. Now write your new helper class M4U_Customer_Helper_Data and define all other override methods

class M4U_Customer_Helper_Data extends Mage_Customer_Helper_Data
{
   // override existing method
  * Retrieve customer register form post url
  public function getRegisterPostUrl()
    {
        return $this->_getUrl('customer/account/create2');
    }

    //write new function
    public function getRegisterPostUrl2()
    {
        return $this->_getUrl('customer/account/createpost');
    }
}

I think who is familiar with Magento override theory, helper override is easy for them. Just try your self. If you face any problem then just make a post. I will try to help you.