Magento – magento how to change the default store in multi store setup

The short and ugly version is to hard code the id of the website and make an if statement in the template.

<?php if (Mage::app()->getWebsite()->getId() == 4) : ?>
    Special logo and link here
<?php else : ?>
    Default behavior here
<?php endif;?>

The long an clean version is to add a configuration flag with scope website (or store view) and if that is set to 'yes' then display the custom logo and link.
Add something like this in system.xml

<config>
    <sections>
        ...
            <web>
                 <groups>
                     <custom_header translate="label">
                         <label>Custom header</label>
                         <frontend_type>text</frontend_type>
                         <sort_order>100</sort_order>
                         <show_in_default>1</show_in_default>
                         <show_in_website>1</show_in_website>
                         <show_in_store>1</show_in_store>
                         <fields> 
                             <custom_link translate="label">
                                 <label>Use custom header link</label>
                                 <frontend_type>select</frontend_type>
                                 <source_model>adminhtml/system_config_source_yesno</source_model>
                                 <sort_order>100</sort_order>
                                 <show_in_default>1</show_in_default>
                                 <show_in_website>1</show_in_website>
                                 <show_in_store>1</show_in_store>
                             </custom_link>
                         </fields>
                     </custom_header>
                 </groups>
             </web>
            ....
    </sections>
</config>

If you add it like this you should find your flag in the Web tab from System->Configuration.
Now you can add this in your template:

<?php if (Mage::getStoreConfigFlag('web/custom_header/custom_link')) : ?>
    Special logo and link here
<?php else : ?>
    Default behavior here
<?php endif;?>

And you can choose from the configuration panel which store has the custom link and logo.

First of all, you don't need to do any changes in index.php. An example apache configuration that you can add at the top of your .htaccess file is:

SetEnv MAGE_RUN_TYPE website
SetEnvIf Host magento\.zweitedomain\.de MAGE_RUN_CODE=zweitewebsite

(if zweitewebsite is the code of your second website)

I usally don't add the ^ and $ delimiters, so that all subdomains or developer instances are matched as well as long the host contains "magento.zweitedomain.de":

• www.magento.zweitedomain.de
• test.magento.zweitedomain.de
• magento.zweitedomain.de.local