backbone.js save()回调总是错误

[yanghu612]

var man = new Man;  
      //实例更改属性  
      man.set({name:"andy"});  
      //save会执行Backbone.sync 若model定义了sync则不会执行服务器请求  
      man.save({success:function(model,response){  
          console.log(model.toJSON().name);
          console.log("ok"); 
      }},{error:function(model,response){  
          console.log(model.toJSON().name);
          console.log("err");  
          }});  

<?php

header('Access-Control-Allow-Origin: *');
header('Content-Type: application/json; charset=utf-8');  
    //不能通过$_POST获取。因为$_POST['paramName'] 只能接收Content-Type: application/x-www-form-urlencoded提交的数据
    $man = json_decode(file_get_contents("php://input"));
    $array=array($man->name,$man->author,$man->price,$man->des);
    file_put_contents("data.txt",$man->name);
    echo file_get_contents("php://input");
?>

能接收到返回的数据，但是总是回调error方法