title: Add custom fields while add/edit wordpress category
body: <p>I am using <strong>WP-3.5.1</strong> and want to know how can we add more custom fields (image, radio, check-box, drop-down) while adding/editing category?</p>
  
  <p>I found <a href="http://en.bainternet.info/2011/wordpress-category-extra-fields" rel="nofollow">http://en.bainternet.info/2011/wordpress-category-extra-fields</a> but first here author did not mention </p>
  
  <blockquote>
    <p>Where to add his code?</p>
    
    <p>For which version of wp this code be use?</p>
    
    <p>What affect if we upgrade to latest version?</p>
    
    <p>What must be pass <code>extra_category_fields( $tag )</code> in?</p>
  </blockquote>
  
  <p>so I start from <strong>wp-admin/edit-tags.php</strong> and paste his code right after where <strong>Slug</strong> field is defined but stuck on <strong>$tag</strong> what should be pass here?</p>
  
  <p>Is there any plugin to add custom fields in category like <strong>More Field</strong> which is for posts?</p>