title: Extend the same class with 2 modules? Magento module conflict?
body: <p>Im trying to make a module that changes the title of a page, my module works fine until I enable another module called </p>
  
  <p>Yoast_CanonicalUrl.</p>
  
  <p>The Yoast module does not touch any of the title methods but does extend the same class as my module: Mage_Page_Block_Html_Head{}</p>
  
  <p>I have tried extending the yoast class if it exists but my module ceases to function once the yoast module is enabled.</p>
  
  <p>I have looked though yoasts code to see if his methods confict with mine and they dont.</p>
  
  <p>Just seems as soon as Yoast is loaded my code just isnt loaded anymore :(</p>
  
  <p>Here is my Head.php:</p>
  
  <pre><code>&lt;?php
  
  if (!(string)Mage::getConfig()-&gt;getModuleConfig('Yoast_CanonicalUrl')-&gt;active == 'true')
  {
    class Yoast_CanonicalUrl_Block_Head extends Mage_Page_Block_Html_Head{}
  }
  class Company_MetaKeyManager_Block_Head extends Yoast_CanonicalUrl_Block_Head
  {
      public function setTitle($title)
      {
          $this-&gt;_data['title'] = Mage::getStoreConfig('design/head/title_prefix') . ' ' . $title
              . ' ' . Mage::getStoreConfig('design/head/title_suffix');
          return $this;
      }
      public function getTitle()
      {
          if (empty($this-&gt;_data['title'])) {
              $this-&gt;_data['title'] = $this-&gt;getDefaultTitle();
          }
          return htmlspecialchars(html_entity_decode(trim($this-&gt;_data['title']), ENT_QUOTES, 'UTF-8'));
      }
      public function getDefaultTitle()
      {
          return 'Hello World';
      }
  } 
  </code></pre>
  
  <p>Here is my Config.xml:</p>
  
  <pre><code>&lt;?xml version="1.0"?&gt;
  &lt;config&gt;
      &lt;modules&gt;
          &lt;Company_MetaKeyManager&gt;
              &lt;version&gt;0.1.0&lt;/version&gt;
          &lt;/Company_MetaKeyManager&gt;
      &lt;/modules&gt;
      &lt;global&gt;
          &lt;blocks&gt;
              &lt;MetaKeyManager&gt;
                  &lt;class&gt;Company_MetaKeyManager_Block&lt;/class&gt;
              &lt;/MetaKeyManager&gt;
              &lt;page&gt;
                  &lt;rewrite&gt;
                      &lt;html_head&gt;Company_MetaKeyManager_Block_Head&lt;/html_head&gt;
                  &lt;/rewrite&gt;
              &lt;/page&gt;
          &lt;/blocks&gt;
          &lt;helpers&gt;
              &lt;MetaKeyManager&gt;
                  &lt;class&gt;Company_MetaKeyManager_Helper&lt;/class&gt;
              &lt;/MetaKeyManager&gt;
          &lt;/helpers&gt;
      &lt;/global&gt;
  &lt;/config&gt;
  </code></pre>
  
  <p>Anyone have any suggestions as to why this happens?</p>