title: How to create <content:encoded> in RSS
body: <p>My RSS create by php like this:</p>
  
  <pre><code>&lt;?php
  include('dataservice.php');
  include('data/article.php');
  include('bussiness/article.php');
  function sumary($string,$len)
  {
      if($len &gt; strlen($string)){$len=strlen($string);};
      $pos = strpos($string, ' ', $len);
      if($pos){$string = substr($string,0,$pos);}else{$string = substr($string,0,$len);}    
      return $string." ...";
  }
  $article = new articlebs();
      $data_article = $article-&gt;Getdata(); 
      $Sum = $data_article == false ? 0 : count($data_article);
      if($Sum!= 0)
      {
          header('Content-Type: text/xml; charset=utf-8'."\n");
  
          echo ('&lt;rss xmlns:slash="http://purl.org/rss/1.0/modules/slash/" version="2.0"&gt;'."\n");
          echo ('&lt;channel&gt;'."\n"); 
          echo('&lt;title&gt;Test&lt;/title&gt;'."\n");
          echo('&lt;link&gt;http://localhost&lt;/link&gt;'."\n");
          echo('&lt;description&gt;Test RSS&lt;/description&gt;'."\n");
  
          for($i = 0; $i &lt; $Sum; $i++)
          {
              $Id_Article = $data_article[$i]['Id_Article'];
              $Title   = $data_article[$i]['Title'];
              $Content   = $data_article[$i]['Content'];
              $Time   = $data_article[$i]['Time'];
              $Id_User   = $data_article[$i]['Id_User'];
  
              preg_match('/&lt;img.+src=[\'"](?P&lt;src&gt;.+)[\'"].*&gt;/i', $Content, $image);
  
              $image = preg_replace( '/(width|height)="\d*"\s/', "", $image );
              $image = preg_replace( '/"/', "", $image );
              $image = preg_replace( '/height=\d*/', "", $image );
              $image = preg_replace( '/(width|height)=\d*/', "", $image );
  
              echo('&lt;item&gt;'."\n");
  
              echo ('&lt;title&gt;').$Title.('&lt;/title&gt;'."\n");
              if( empty( $image ) )
              {
                  echo  ('&lt;image&gt;http://localhost/images/noimg.jpg&lt;/image&gt;'."\n");
              }
              else
              {
                  echo ('&lt;image&gt;'). $image['src'].('&lt;/image&gt;'."\n");
              }  
              echo ('&lt;link&gt;&lt;![CDATA[')."http://localhost/index.php?detail&amp;id=".$Id_Article.(']]&gt;&lt;/link&gt;'."\n");
              echo ('&lt;pubDate&gt;').$Time.('&lt;/pubDate&gt;'."\n"); 
              echo ('&lt;guid&gt;&lt;![CDATA[').$Content.(']]&gt;&lt;/guid&gt;'."\n"); 
              echo ('&lt;description&gt;&lt;![CDATA[');
              echo strip_tags(sumary($Content,500));
              echo (']]&gt;&lt;/description&gt;'."\n");
              echo ('&lt;content:encoded&gt; &lt;![CDATA['.$Content.']]&gt; &lt;/content:encoded&gt;'); // i think error here
              echo ('&lt;/item&gt;'."\n");
  
          }
          echo ('&lt;/channel&gt;'."\n");
          echo ('&lt;/rss&gt;');
      }
    ?&gt;
  </code></pre>
  
  <p>When i run this RSS, it give an error:</p>
  
  <blockquote>
    <p>Namespace prefix content on encoded is not defined.</p>
  </blockquote>
  
  <p>I try to Google it but i have not find the way to fix it. 
  Please help me fix it. Thank you so much</p>