说一下原理：
后台：计算各个类型的评论总和和全部评论。
后台函数代码：
/*统计评论*/
function getcccount($goods_id){
$sql="SELECT count(id_value) FROM ". $GLOBALS['ecs']->table('comment') ." WHERE id_value = $goods_id AND comment_rank!=0  and select_type=0 and parent_id=0";
$count = $GLOBALS['db']->getOne($sql);
if(empty($count)){
return '没有评论';
}
else
{
$sql="SELECT count(id_value) FROM ". $GLOBALS['ecs']->table('comment') ." WHERE id_value = $goods_id AND comment_rank =5 and select_type=0 and parent_id=0";
$count5 = $GLOBALS['db']->getOne($sql);

$sql="SELECT count(id_value) FROM ". $GLOBALS['ecs']->table('comment') ." WHERE id_value = $goods_id AND comment_rank =1 and select_type=0 and parent_id=0";

$count1 = $GLOBALS['db']->getOne($sql);

$sql="SELECT count(id_value) FROM ". $GLOBALS['ecs']->table('comment') ." WHERE id_value = $goods_id  and select_type=0 and parent_id=0 AND comment_rank BETWEEN 2 AND 4";
$count3 = $GLOBALS['db']->getOne($sql);

$hb =percent($count5,$count);
$zb =percent( $count3,$count);
$cb =percent($count1,$count);
$arr=array();
$arr['all']=$count;   //统计全部评论
$arr['hao']=$count5;  //统计好评个数
$arr['zhong']=$count3;  //统计中评个数
$arr['cha']=$count1 ;  //统计差评个数
$arr['hb']=$hb; //好评百分比
$arr['zb']=$zb; //中评百分比
$arr['cb']=$cb; //差评百分比
return $arr;
}
}

/*百分比计算函数
*$p 被除数
*$t 总个数
*/
function percent($p,$t){
return sprintf('%.2f%%',$p/$t*100);
}