WordPress为非友情链接添加nofollow属性的方法

<tr>
  <th scope="row">nofollow</th>   
  <td>
    <fieldset>
      <legend class="screen-reader-text"><span> nofollow </span></legend> 
      <label for="nofollow"><input class="valinp" type="checkbox" name="nofollow" value="nofollow" id="nofollow" <?php xfn_check('nofollow'); ?> />nofollow</label>
    </fieldset>
  </td>
</tr>

/*
Plugin Name: Add-nofollow-to-XFN
Plugin URI: http://www.slyar.com/blog/Add-nofollow-to-XFN
Description: 在后台链接管理的XFN关系中添加一个 nofollow 标签
Author: Slyar
Version: 1.2
Author URI: http://www.slyar.com/
*/
function admin_xfn() {?>
<script type="text/javascript">
addLoadEvent(addNofollowTag);
function addNofollowTag() {
  tables = document.getElementsByTagName('table');
  for(i=0;i<tables.length;i++) {
    if(tables[i].getAttribute("class") == "links-table") {
      tr = tables[i].insertRow(1);
      th = document.createElement('th');
      th.setAttribute('scope','row');
      th.appendChild(document.createTextNode('Follow'));
      td = document.createElement('td');
      tr.appendChild(th);
      label = document.createElement('label');
      input = document.createElement('input');
      input.setAttribute('type','checkbox');
      input.setAttribute('id','nofollow');
      input.setAttribute('value','nofollow');
      label.appendChild(input);
      label.appendChild(document.createTextNode(' nofollow'));
      td.appendChild(label);
      tr.appendChild(td);
      input.name = 'nofollow';
      input.className = 'valinp';
      if (document.getElementById('link_rel').value.indexOf('nofollow') != -1) {
        input.setAttribute('checked','checked');
      }
      return;
    }
  }
}
</script>
<?php
}
add_action('admin_head','admin_xfn');

/**
 * 一下两个钩子是为了保证代码只在links页面显示
 * 如果你想了解更多load-$page action的信息，访问http://codex.wordpress.org/Adding_Administration_Menus#Page_Hook_Suffix
 */
add_action('load-link.php', 'sola_blogroll_nofollow');
add_action('load-link-add.php', 'sola_blogroll_nofollow');

function sola_blogroll_nofollow() {
    //通过action add_meta_boxes创建我们需要的Meta Box
    add_action('add_meta_boxes', 'sola_blogroll_add_meta_box', 1, 1);
    //通过filter pre_link_rel将数据保存
    add_filter('pre_link_rel', 'sola_blogroll_save_meta_box', 10, 1);
}

//创建Nofollow Meta Box
function sola_blogroll_add_meta_box() {
    //翻译成中文就是，创建一个名叫Blogroll Nofollow的Meta Box，放在link页面的右侧边栏，Meta Box的结构
    //由函数sola_blogroll_inner_meta_box产生
    add_meta_box('sola_blogroll_nofollow_div', __('Blogroll Nofollow'), 'sola_blogroll_inner_meta_box', 'link', 'side');
}

//输出Meta Box的HTML结构
function sola_blogroll_inner_meta_box($post) {
    $bookmark = get_bookmark($post->ID, 'ARRAY_A');
    if (strpos($bookmark['link_rel'], 'nofollow') !== FALSE)
        $checked = ' checked="checked"';
    else
        $checked = '';
    ?>
    <label for="sola_blogroll_nofollow_checkbox"><?php echo __('Nofollow this link?'); ?></label>
    <input value="1" id="sola_blogroll_nofollow_checkbox" name="sola_blogroll_nofollow_checkbox"<?php echo $disabled; ?> type="checkbox"<?php echo $checked; ?> /> <?php echo $message; ?>
    <?php
}

//保存用户的选择
function sola_blogroll_save_meta_box($link_rel) {
    $rel = trim(str_replace('nofollow', '', $link_rel));
    if ($_POST['sola_blogroll_nofollow_checkbox'])
        $rel .= ' nofollow';
    return trim($rel);
}