PHP和AJAX的问题.....请高手!~


            <tr>
              <td valign=\"top\" nowrap=\"nowrap\" align=\"right\" width=\"90\">消费感受：<br />
              (1000字以内)</td>
              <td>
  <textarea name=\"pingcontent\" id=\"pingcontent\" rows=\"8\" cols=\"48\"></textarea>
          <div id=\"pingcontent\" style=\"display:inline\"></div>   </td>
            </tr>
            <tr>
              <td colspan=\"2\" align=\"center\" valign=\"top\" nowrap=\"nowrap\">
  <input name=\"button\" type=\"button\" id=\"BtnAdd\" onclick=\"lcs()\" value=\"  提交点评  \" language=\"javascript\" />
  <input type=\"hidden\" id=\"id_q\" value=\"$shopid\" name=\"id_q\" />
  </td>
            </tr>
          </table></form>
        </div>
        
       ==========================================================================
"提交点评"的按钮按下去没有任何反应,,这是什么问题?>>>>>>>>>>>>>>>>>>>>>>>>附: \"lcs()\"  JS代码:function lcs(){
 
  if($('pingcontent').value.length < 15) {       
alert("对不起，‘评论’内容不能少能少于15个字！");
       return false;                                                                          
   }     var opt = {
    method: 'post',
    postBody: 'quality='+$("quality").value+'&condition='+$("condition").value+'&service='+$("service").value+'&costmembers='+$("costmembers").value+'&costmoney='+$("costmoney").value+'&pingcontent='+$("pingcontent").value+'&taginput='+$("tags").value+'&sid='+$("id_q").value+'&ttt=1',
    onSuccess: udc
}
new Ajax.Request('/shop_comm_new_save.php', opt);
}