php:在服务器上实时运行时会话不工作

我正在做一个PHP项目。我有一个奇怪的错误。我的PHP项目在本地服务器（WAMP服务器）上运行良好。但在实时服务器上托管后，它就不起作用了。

问题：在Login.php页面上创建的会话变量未在Report.php页面上传递值。代码如下：

登录.php

<?php
$con=mysql_connect("mysql51****************","username","password")or die(mysql_error());
$select_db=mysql_select_db("database_name",$con);
$error="";
if(isset($_POST['submit']))
{
    $userid=mysql_real_escape_string($_POST['username']);
    $password=mysql_real_escape_string($_POST['password']);
    $sql="SELECT * FROM user_details WHERE user_name='{$userid}' AND password='{$password}' ";
    $result = mysql_query($sql);
    if(mysql_num_rows($result) <= 0)
    {
        $error="Invalid UserId or Password.";
    }
    else
    {
        //session_set_cookie_params(60*60*60, '/', '.abcxyz.com');
        ini_set('session.cookie_domain','.abcxyz.com');
    session_start();
    //$userid=mysql_real_escape_string($_POST['abc']);
    //echo($userid);
    $_SESSION['user']=$userid;
    $_SESSION['userid']="true";
    //echo $_SESSION['userid'];
    $error="Successfully Login";
    //header("Location: admin.php?page=report");
    /*echo '<script type="text/javascript">alert("header is not working.' . $_SESSION['user'] . '");</script>';
*/  ?>
    <script type="text/javascript">
        /*alert("Please select a Source And Destination Country");  */
        window.location.href='admin.php?page=report';
    </script>       
<?php
    }
}
?>
<br />
  <h1 style="text-align:center">Login</h1>
  <form  class="login"  action="login.php" method="post" name="form1" id="form1">
  <p>Username:</p>
      <input class="login-input" type="text" name="username" value=""/>
    <p> Password : </p>
      <input class="login-input" type="password" name="password" value=""/>
  <p>
    <p style="color:#F00; font-size:12px; font-weight:100"><?php echo htmlentities($error); ?>  </p>
    <input  class="login-submit" type="submit" name="submit" value="Login"/>    
</form>

Report.php

<?php
include("connections/Connections.php");
/*$con=mysql_connect("localhost","admin","")or die(mysql_error());
$select_db=mysql_select_db("test",$con);*/
/*session_start();
if(session_is_registered('test'))
{
    echo"registered";
}
else
{
    header("Location: login.php");
}*/
//$user=$_SESSION['userid'];
$user=$_SESSION['userid'];
echo '<script type="text/javascript">alert("header is not working.' .$user . '");</script>';
if($user=="true")
{
    //echo " Logining Successfully.";
}
else
{
    ?>
    <script type="text/javascript">
        //alert("Please select a Source And Destination Country");  
        window.location.href='login.php';
    </script>
<?php
    //header("Location: login.php");
}
?>
<?php
/*session_start();
$user=$_SESSION['userid'];
echo($user);
if($user=="Admin")
{
    echo " Logining Successfully.";*/
$sql="SELECT * FROM register ";
if(isset($_POST['btnfilter']))
{
    $search_term=mysql_real_escape_string($_POST['search_text']);
    $answer = $_POST['filter'];  
    if ($answer == "ID") {          
        $sql .="WHERE id= '{$search_term}' ";
    }
    elseif ($answer == "Name") {          
        $sql .="WHERE fullname Like '%{$search_term}%'";
    }
    elseif ($answer == "DOB") {          
        $sql .="WHERE dob Like '%{$search_term}%' ";
    }
    elseif ($answer == "Occupation") {          
        $sql .="WHERE occupation Like '%{$search_term}%' ";
    }
    else
    {
        echo("Pealse Enter a valid value"); 
    }
}
elseif(isset($_POST['btnrmfilter']))
{
    $sql="SELECT * FROM register";
}
$query=mysql_query($sql) or die(mysql_errno());
//}
/*else
{
    header('Location: /login.php');
}*/
?>
<style type="text/css">
    table
    {
        font-size:12px;border-bottom:1px solid #ccc;
    border-left:1px solid #ccc}
    td 
    { 
    padding:5px 3px;
    border-top:1px solid #ccc;
    border-right:1px solid #ccc}
</style>
  <div class="content">
  <h1>Data Reading From database.</h1>
  <form id="search_form" method="post" action="">
  <div class="radio">
      <input type="radio" name="filter" value="ID" />ID
      <input type="radio" name="filter" value="Name" />Name
      <input type="radio" name="filter" value="DOB"/>DOB
      <input type="radio" name="filter" value="Occupation"/>Occupation<br />
  </div>
  <div class="input" >
      <input   type="text" name="search_text" value=""/>
      <input  type="submit" value="FilterData" name="btnfilter" />     
      <input  type="submit" value="RemoveFilter" name="btnrmfilter" />
  </div>
  </form>
    <table border="0" cellpadding="0" cellspacing="0">
     <colgroup> 
    <col width="2%" style="color:#f60" valign="middle" align="center" >
    <col width="12%" >
    <col width="8%" >
    <col width="5%" align="center" >
    <col width="10%" >
    </colgroup>
      <tr style="background:#eee; height:30px;">
        <td>ID</td>
        <td>Name</td>
        <td>DOB</td>
        <td>Nationality</td>
        <td>Mobile No</td>
        <td>Phone No</td>
        <td>Email</td>
        <td>Education</td>
        <td>Occupation</td>
        <td>Comment</td>
        <td >Noofexp</td>
      </tr>
        <?php while($row = mysql_fetch_array($query)) { ?>
          <tr>
          <td><?php echo $row['id']; ?></td>
          <td><?php echo $row['fullname']; ?></td>
          <td><?php echo $row['dob']; ?></td>
          <td><?php echo $row['nationality']; ?></td>
          <td><?php echo $row['mobno']; ?></td>
          <td><?php echo $row['phno']; ?></td>
          <td><?php echo $row['email']; ?></td>
          <td><?php echo $row['education']; ?></td>
          <td><?php echo $row['occupation']; ?></td>
          <td><?php echo $row['comment']; ?></td>
          <td><?php echo $row['noofexp']; ?></td>
        </tr>
        <?php } ?>
    </table>
    <h2>&nbsp;</h2>
    <h3>Thanks for view.</h3>
    <!-- end .content --></div>
  <div class="footer">
    <p>Footer</p>
<!-- end .footer --></div>
  <!-- end .container --></div>
</body>
</html>

编辑：

正如答案所示，我编辑如下：

Login.php:

<?php
session_start();
$con=mysql_connect("mysql51*************","username","password")or die(mysql_error());...
...

Report.php：

<?php
session_start();
include("connections/Connections.php");...
...

但是我仍然没有得到Report.php中的会话变量值。