Php 刚刚清除了缓存和cookies，现在我有以下错误

再次感谢那些建议和帮助我编写代码的人。不幸的是，在我清除缓存和cookies之前，一切都很顺利。有3个以前没有的错误。以下错误是：

注意：未定义变量：第29行C:\xampp\htdocs\Assignment\u 3\login.php中的用户名 注意：未定义变量：第34行C:\xampp\htdocs\Assignment\u 3\login.php中的用户名 警告：会话_start（）：会话id太长或包含非法字符，有效字符为第37行C:\xampp\htdocs\Assignment_3\login.php中的a-z、a-z、0-9和“-，”

前两个是一个惊喜，因为我发誓我解决了这个问题。另一方面，最后一个错误对我来说是全新的。我以前从来没有遇到过这个问题。我将发布我的login.php以获得更好的参考。再次感谢您的帮助

login.php

<?php



//GOT USER ID COOKIE? IF SO GET IT
if(isset($_COOKIE["userid"])) {
    $username = $_COOKIE["userid"];
}
//NO USER ID? GET THE COOKIE
else {

    //SET COOKIE, EXPIRE IN 600 SECONDS
    setcookie("userid", $username, time()+600 );

}

//SESSION ID IS OUR UNIQUE COOKIE
session_id($username);

//STARTING SESSION
session_start();

$_SESSION['logged_in'] = true;

//TOTAL AMOUNT OF TIME USER WAS LOGGED IN
$_SESSION['time_logged_in'] = time();


//THIS PAGE WILL PROMPT THE USER TO LOGIN WITH AN ALREADY REGISTERED USERNAME AND PASSWORD IN THE DATABASE
//IT WILL CHECK IN THE DATABASE TO SEE IF THE USERNAME AND PASSWORD ARE IN THE SAME ARRAY
//IF NOT THEN IT WILL SAY LOGIN FAILE.

//INCLUDE FUNCTIONS
include "functions.inc";

//IF THE ERRORS ARE SET TO FALSE, ECHO THE ERROR MESSAGES
if (!isset($errors)) $errors = array();

//INITIATE VARIABLE TO ACCESS THE USER DATABASE
$userfile = "user_data.dat";
$currentuser = "curren_user.dat";

//IF THE LOGIN BUTTON WAS PRESSED THEN VALIDATE THAT THE USER AND PASSWORD ARE IN THE SAME ARRAY
//IF NOT, THEN ECHO ERROR MESSAGE.
//IF THEY MATCH, THEN GO TO THE SUCCESSFUL LOGIN PAGE.
if (array_key_exists("login_btn", $_POST))
{
    $logins = arrayfile_to_array($userfile);
    $userlogin = $_POST['user'];



    if (validate_login(strtolower($userlogin['name']), $userlogin['pass'], $logins))
    {
        $errors['login'] = "Invalid Login";
        //break; taken out 11/9/2013
    }
    if (count($errors) == null)
    {
        //QUESTIONABLE VARIABLE
        $_SESSION['username'] = $userlogin['name'];
        header("Location: success_login.php");
    }
}


//IF THE USER HITS THE REGISTER NEW USER BUTTON,
//THEN TAKES THEM TO THE REGISTER NEW USER PAGE.
if (array_key_exists("register_btn", $_POST))
{
    header("Location: registration_page.php");
}

//PRINTING THE LOGIN USER INPUT FORMS.
//INCLUDES USERNAME AND PASSWORD.
//IF USERNAME AND PASSWORD DO NOT MATCH,
//HAS STUCKY FORM AND WILL ECHO ERROR MESSAGE AT TOP.
?>


<center>

<H1>Log In</H1>

<?php if (isset($errors['login'])) echo " <font color='red'>{$errors['login']}</font>"; ?>

<form method="POST" action="login.php"> 
    <table>
    <!--Text input for login-->
    <tr><td>Username:</td>
    <td><input type = 'TEXT'
           name = 'user[name]'
           value = '<?php  if(isset($_POST["user"])) {$tmp = $_POST["user"]; echo $tmp["name"]; } ?>'></td></tr>
    <br>
    <tr><td>Password:</td>
    <!--Password input for new password-->
    <td><input type = 'PASSWORD'
           name = 'user[pass]'
           value = '<?php  if(isset($_POST["user"])) {$tmp = $_POST["user"]; echo $tmp["pass"]; } ?>'></td></tr>
    <br>
    <tr></tr>
    <br>
    <!--Button to go back to form to fill again after errors are realized-->
    <tr><td><input type = 'SUBMIT'
         name = 'login_btn'
         value = 'Login'></td>
    <br>
    <!--Button to go back to form to fill again after errors are realized-->
    <td><input type = 'SUBMIT'
         name = 'register_btn'
         value = 'Register New User'></td></tr>    
    </table>
</form>

</center>
<?php 
//CLEARS THE ERRORS ARRAY
$errors = array(); 
?>

登录
行中：

else {
//SET COOKIE, EXPIRE IN 600 SECONDS
setcookie("userid", $username, time()+600 );

您正试图在userid中分配一个名为
$username
的变量。
但我在任何地方都看不到它

如果未定义，那么问题就出在哪里。
用户名在这里设置在哪里setcookie（“userid”，$username，time（）+600）？如果尚未从表单中捕获用户，可能不想设置用户名？即使从表单中获取用户名，您确定应该在验证之前设置用户名吗？如果他们输入错误怎么办？在会话的生命周期内，它将在会话中设置不正确。