Magento: Add configuration menu item in the admin configrations

To add a configuration menu for a custom module in the admin configurations, you create or modify 4 files, adminhtml.xml, system.xml, config.xml and Data.php.
For demonstration, we will add a configuration menu item for an existing helloworld module and you can use the configuration page
in the admin panel to set the greeting text.

1. app/local/MyExtensions/Helloworld/etc/adminhtml.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <acl>
        <resources>
            <admin>
                <children>
                    <system>
                        <children>
                            <config>
                                <children>
                                    <helloworld_setting>
                                        <title>Hello World</title>
                                    </helloworld_setting>
                                </children>
                            </config>
                        </children>
                    </system>
                </children>
            </admin>
        </resources>
    </acl>
</config>

2. app/local/MyExtensions/Helloworld/etc/system.xml

<?xml version="1.0" encoding="UTF-8"?>
<config>
    <tabs>
        <helloworld translate="label" module="helloworld">
            <label>Hello World</label>
            <sort_order>99999</sort_order>
        </helloworld>
    </tabs>
    <sections>
        <helloworld_setting translate="label" module="helloworld">
            <label>Settings</label>
            <tab>helloworld</tab>
            <frontend_type>text</frontend_type>
            <sort_order>99</sort_order>
            <show_in_default>1</show_in_default>
            <show_in_website>1</show_in_website>
            <show_in_store>1</show_in_store>
            <groups>
                <greeting_settings translate="label">
                    <label>Greeting Settings</label>
                    <frontend_type>text</frontend_type>
                    <sort_order>1</sort_order>
                    <show_in_default>1</show_in_default>
                    <show_in_website>1</show_in_website>
                    <show_in_store>1</show_in_store>
                    <fields>
                        <enabled translate="label">
                            <label>Enabled</label>
                            <frontend_type>select</frontend_type>
                            <source_model>adminhtml/system_config_source_yesno</source_model>
                            <sort_order>10</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                        </enabled>
                        <greeting translate="label,comment">
                            <label>Greeting</label>
                            <frontend_type>text</frontend_type>
                            <sort_order>20</sort_order>
                            <show_in_default>1</show_in_default>
                            <show_in_website>1</show_in_website>
                            <show_in_store>1</show_in_store>
                            <comment>Greeting text.</comment>
                        </greeting>
                    </fields>
                </greeting_settings>
            </groups>
        </helloworld_setting>
    </sections>
</config>

3. app/local/MyExtensions/Helloworld/etc/config.xml, you need to add the below in the global tag to specify the helper class

    <helpers>
        <helloworld>
            <class>MyExtensions_Helloworld_Helper</class>
        </helloworld>
    </helpers> 

4. app/local/MyExtensions/Helloworld/Helper/Data.php, this file can be empty but it just have to be there in order to be able to navigate to the helloworld configration page.

<?php
class MyExtensions_Helloworld_Helper_Data extends Mage_Core_Helper_Abstract {
	
}
?>

5. Clear the cache if you haven’t done so.

6. With the above 4 files in place and the cache cleared. We can now go to the helloworld configuration page by
Login to Admin Panel as an adminstrator -> System -> Configuration -> Settings under Hello World in the left Configuration menu -> Greeting Settings -> Enter some greeting text -> Save Config

7. To get the text we set in step 6.

//sectionName/groupName/fieldName
echo Mage::getStoreConfig('helloworld_setting/greeting_settings/enabled');
echo Mage::getStoreConfig('helloworld_setting/greeting_settings/greeting');