代码如下：

<?php 
/** 
 * 获取Gravatar头像 
 */ 
function getGravatar_fk($email, $s = 40, $d = 'mm', $g = 'g') { 
 $hash = md5($email); 
 $avatar = "http://gravatar.duoshuo.com/avatar/$hash?s=$s&d=$d&r=$g"; 
 return $avatar; 
} 
//获取最新评论访客 
function comment($num){ 
 $t = MySql::getInstance(); 
 $sql = "SELECT * FROM ".DB_PREFIX."comment WHERE mail != '' ORDER BY `cid` DESC LIMIT $num"; 
 $list = $t->query($sql); 
 while($row = $t->fetch_array($list)){ 
  $i = '<li><a rel="nofollow" href="'.$row['url'].'"><img src="'.getGravatar_fk($row['mail']).'"></a></li>'; 
  echo $i; 
 } 
} 
 ?> 

在需要的地方调用：<?php comment($num) //$num为调用数量 ?>