How to make the custom module effect on the node and only one content type? The following code is used to output five images, according to what's number contained in $fen. I want to put the button in nodes of a specific content type (e.g. "company").
Which code should I use in my module to get this?

&lt;form action="" method="get"&gt;
&lt;input type="submit" name="fen" /&gt;
&lt;/form&gt;
&lt;?php
  $star = getStar($_GET['fen']);        
  echo "&lt;img src=\"xing_$xin.jpg\" /&gt;";

  function getStar($fen) {
    if ($fen &lt; 10) {
        return 1;
    }
    elseif ($fen &lt; 100) {
      return 2;
    }
    elseif ($fen &lt; 1000) {
      return 3;
    }
    elseif ($fen &lt; 10000) {
      return 4;
    }
    else {
      return 5;
    }
  }
?&gt;
If you want to add content to nodes, you can in drupal 6 use the hook_nodeapi where op is view.

As you get the node object, you can detect the node type ect. You would need to add something like this to your module

module_nodeapi(&amp;$node, $op, $a3 = NULL, $a4 = NULL) {
  switch($op) {
    case 'view':
      if ($node-&gt;type == 'node_type') {
        // $a3 indicates if teaser
        // $a4 indicates if page
        $node-&gt;content['my_additional_field'] = array(
          '#value' =&gt; 'HTML', // create html with theme or form function. 
          '#weight' =&gt; 10,
        );
      }
      break;
  }
}