php - Ajax post json响应问题

Question

我的 ajax 响应有问题。我正在使用自定义查询从数据库中获取结果。当查询成功运行时，Json 响应始终显示空值。这是我的代码:

if(isset($_POST)){

$arr = array();
//$query = mysql_query(" insert into login (user,pass) values ('".$_POST['firstname']."','".$_POST['lastname']."') ") or die('test');

$query = mysql_query(" select * from  login where user = '".$_POST['firstname']."' && pass = '".$_POST['pass']."' ") or die('test');
$rows = mysql_num_rows($query);

    while($fetch = mysql_fetch_array($query))
    {
        if($fetch)
        {
                $_SESSION['ID']= $fetch['id'];
                $arr['id'] = $_SESSION['ID'];

        }
        else
        {
            $arr['failed']= "Login Failed try again....";

        }

}

echo json_encode($arr);

}

Answer 1

@Amandhiman 我不明白 if 语句在 while 中有什么用

if($fetch)
    {
            $_SESSION['ID']= $fetch['id'];
            $arr['id'] = $_SESSION['ID'];

    }

提及代码绝对适合您

    if($rows>0)
    {
        while($fetch = mysql_fetch_array($query))
        {
             $_SESSION['ID']= $fetch['id'];
             $arr['id'] = $_SESSION['ID'];
        }
    }else
        {
            $arr['failed']= "Login Failed try again....";

        }