不需要form了，监听提交按钮的点击事件就可以了，试试jquery，能帮你更快的完成这个功能

不用submit,通过ajax提交。后端返回你需要的字段即可

先导个jq。

function xxxAction() {
    var url = ........;
    $.ajax({
        "url":url,
        "dataType":"text",
        "type":"post",
        "data":{"jsonData":JSON.stringify(getData())},
        "success":function(返回值){
          xxxxx;
        }
    });
}

楼上有好几种替代方案，我呢，给你一个在你基础上改进版本：

<form method="post" action="basicform.php" onsubmit="return save()">
Name: <input type="text" id="name" name="name" size="25" /> <br />
Email: <input type="text" id="email" name="email" size="25" /> <br />
Event ID: <input type="text" id="event_id" name="event_id" size="25" /> <br />
Number of Tickets: <input type="text" id="number_of_tickets" name="number_of_tickets" size="25" /> <br />

<button type="submit">submit</button>
</form>
<p id="output"></p>

var out = document.getElementById('output');
function save(){
  var obj= new XMLHttpRequest();  
  var params = [],
      keys = ['name','email', 'event_id', 'number_of_tickets'];
  for (var idx in keys) {
      params.push(keys[idx] + '=' + document.getElementById(keys[idx]).value)
  }
   obj.open("POST", /*"ajax_data.html"*/"http://guimon.info/js/tickets.php", true); 
   obj.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
 //obj.setRequestHeader("Content-length", params.length);
 //obj.setRequestHeader("Connection", "close");
   obj.onload = function (){ 
  if(obj.status == 200 ){
   var response = JSON.parse(obj.responseText);   
   out.innerHTML += "<p>" + (response.error || response.content) + "</p>";
  } else {
      out.innerHTML = '给我一个吻！';
  }
 };
 obj.send(params.join('&'));
 return false;
}