从php向jquery返回jsonencode错误

如果用户名和密码错误，我想显示错误。我从昨天开始尝试。不知道出了什么问题。每次controll都会出错并显示错误。尝试了json，但不起作用

<script>
$(document).ready(function() {
    $("#LoginForm").submit(function(e) {
        $("#simple-msg1").html("<img  src='img/loading.gif'/>");
        var postData ="";
        postData = $('#LoginForm').serializeArray();
        var formURL = $('#LoginForm').attr("action");
        $.ajax( {
            url : formURL,
            type: "POST",
            data : postData,
            dataType:'json',
            success:function(data, textStatus, jqXHR)  {
                alert(data.error);
                if(data.error == 1) {
                    $("#simple-msg1").html('<pre><code class="prettyprint">'+data.message+'</code>< /pre>');
                } else {
                    $("#simple-msg1").html('<pre><code class="prettyprint"> Login Successfull </code></pre>');
                    window.location = "/property/Dealer/ManageProfile.php?Login=successfull";
                }
            },
            error:function(data,textStatus)  {
                $("#simple-msg1").html('<pre><code class="prettyprint"> wrong username or password 11</code></pre>');
            }
        });
        e.preventDefault(); //STOP default action
    });
    $("#Button1").click(function() {
        $("#LoginForm").submit(); //SUBMIT FORM
    });
});
</script>

这是php文件

<?php
ob_start();
if(session_id() == '')
    {
        session_start();
    }
include 'config.php';
$error = '0';
$message = 'Valid';
$redirect = 'Dealer/EditLoginDetails.php';
$myusername=$_POST['txtusername']; 
$mypassword=$_POST['txtpassword']; 
$myusername = stripslashes($myusername);
$mypassword = stripslashes($mypassword);
$myusername = mysql_real_escape_string($myusername);
$mypassword=mysql_real_escape_string($mypassword);
$qry = "SELECT UserName,Type_user FROM login WHERE UserName = '".$myusername."' AND password = '".$mypassword."' ";
$result = mysql_query($qry) or die ("Query failed");
$UserData = mysql_fetch_array($result);
if($UserData['UserName'] != "") {
    //echo $UserData['UserName'];
    $_SESSION['UserId'] = $myusername;
    $typ = $UserData['Type_user'];
    if ( $typ == "Dealer") { 
        header('location:/Dealer/EditLoginDetails.php');  
        //echo "dealer";
        //echo json_encode(array('success'=>'true'));
        //header('location:/Dealer/EditLoginDetails.php');
    } else if ($typ == "Individual") {
        header('location:/Dealer/EditLoginDetails.php');  
    } else {
        header('location:/Builder/managep.php'); 
    }
} else { 
    $error = '1';
    $message = 'Invalid username or password';
    // echo "forbiddnt";
    //header('HTTP/1.0 403 Forbidden');
    //echo " wrong username or password";
}
echo json_encode(array('error' => $error, 'message' => $message, 'redirect' => $redirect));
?>