In this exercise, we will change the behavior of a block by extending or inheriting the original class and redefining the behavior of a specific function or method. Specifically we will redefine the behavior of function canEmailToFriend().

We want to change the behavior of a class member located in this file
app\code\core\Mage\Catalog\Block\Product\View.php

Our override will be found here:
app\code\local\Msc\Module9\Block\Catalog\Product\View.php

First we want to create a new module structure. See the first tutorial on modules for more details about this step.

in \app\etc\modules\Msc_Module9.xml

<?xml version="1.0"?>
    <config>
      <modules>
        <Msc_Module9>
            <active>true</active>
            <codePool>local</codePool>
         </Msc_Module9>
       </modules>
    </config>

in app\code\local\Msc\Module9\Block\Product\View.php

<?php
Class Msc_Module9_Block_Catalog_Product_View extends Mage_Catalog_Block_Product_View{

    public function canEmailToFriend()
    {    
        // By returning false, we basically eliminate the block.
        return false;
    }
}

in app\code\local\Msc\Module9\etc\config.xml

<?xml version="1.0"?>
<config>
 <modules>
    <Msc_Module9>
        <version>1.0.0</version>
    </Msc_Module9>
 </modules>
<global>
   <blocks>
     <catalog>
         <rewrite>            
             <product_view>Msc_Module9_Block_Catalog_Product_View</product_view>
             </rewrite>
        </catalog>
    </blocks>
 </global>
</config>