AJAX从PHP收到了错误的返回值

Question

所以我是AJAX的新手。我目前正在使用带有PHP的ajax创建动态登录。如果凭证有效，则php函数返回1值，如果不是，则返回0值。但是，现在AJAX似乎永远无法在登录有效时提取值，即使系统实际上是在记录我。

AJAX

   $(document).ready(function(){
  //  $("#add_err").css('display', 'none', 'important');
     $("#login").click(function(){  
          username=$("#login-username").val();
          password=$("#login-password").val();
          $.ajax({
           type: "POST",
           url: "userMGMT/login.php",
           dataType: 'html',
           data: "name="+username+"&pwd="+password,
           success: function(html){    
            if(html=='1')    {
                //document.write("hello");
             $("#add_err").html("right username or password");
             window.location="newgame.php";
            }

            else    {
                //document.write("hellefefo");
            $("#add_err").css('display', 'inline', 'important');
             $("#add_err").html("Wrong username or password");
            }
           },
           beforeSend:function()
           {
            $("#add_err").css('display', 'inline', 'important');
            $("#add_err").html("Loading...")
           }
          });
        return false;
    });
});

PHP

    $username=$_POST['name']; 
$password=$_POST['pwd']; 

$username = stripslashes($username);
$password = stripslashes($password);
$username = mysql_real_escape_string($username);
$password = mysql_real_escape_string($password);
$sql = "SELECT * FROM $tbl_name WHERE username='$username' and password='$password'";
$result = mysql_query($sql);

// Mysql_num_row is counting table row
$count=mysql_num_rows($result);

// If result matched $username and $password, table row must be 1 row
if($count==1){
    echo '1';
    session_start();
    $_SESSION['loggedin'] = true;    
$username = strtolower($username);
    $_SESSION['username'] = $username;
    header( 'Location: uid.php');
}
else
{
    echo '0';
    //header( 'Location: ../404.php?info=The System Couldnt Log You On');
}