Json

对于ajax应用来说，把和控件榜定的数据用json来承载，既可以避免频繁调用httprequest，也可以避免xml带来的性能解释。

假设我们要有一个级联菜单，显示用户组以及下面的用户，我们可以这样做

      $group_user = Array();   
      $groups = $db->getAll("select * from $dbutils->group");

      for ($i = 0, $count = count($groups); $i < $count; $i++) {
     
         $users = $db->getAll("select * from $dbutils->user_group ug,$dbutils->user u where ug.user_id = u.user_id and ug.group_id = ".$groups[$i]['group_id']);
         $group_user[$groups[$i]['group_id']]['users'] = $users;
      }

      $json = new JSON(JSON_LOOSE_TYPE);
      $group_user_json_data = $json->encode($group_user);  //将数据从php数组转换成javascript数组
     

     
      $group_user_javascript_data = '<script type="text/javascript">' . "/n"
   . '<!-- // associated javascript data' . "/n"
   . 'var group_user_json_data = '
   . $group_user_json_data . ";/n"
   . '-->' . "/n"
   . '</script>';

 

在模板表单里面

<?php

 echo $group_user_javascript_data;    //把json的数据显示出来
 

?>

<script language="javascript" type="text/javascript" >
 
function addOptions(optionList, optionMenu)
{
 removeOptions(optionMenu);  // clear out the options
 for (var i=0; i < optionList.length; i++) {
  
   optionMenu[i] = new Option(optionList[i].truename, optionList[i].user_id);

  }

}

 

function removeOptions(optionMenu)
{
  len = optionMenu.options.length;
  for (var i=len-1; i >=0 ; i--) {
  
    optionMenu.options[i] = null;

  }

}

 
function change_group() {

  var users = group_user_json_data[document.getElementById('receive_group').value]['users'];//从json里面得到对象

  addOptions(users, document.getElementById('receive_user'))

 
  
}
</script>

 

                                    <tr>
                                      <td width="10%" >接收部门</td>
                                      <td width="80%"><select name="receive_group" onchange="change_group()"><?php echo build_group_select(''); ?></select></td>
                                     </tr> 
                                    <tr>
                                      <td>接收人</td>
                                      <td><select name="receive_user" id="receive_user"></select></td>
                                     </tr>