不显示我的会话以回声

我有 2 个不同的.php文件。在第一个 php 文件中，您选择要显示的联赛。第二个 php 文件显示您点击的第一个联赛的球队。我已经设置了一个会话变量，但它显示了一个空白页。为什么？法典：联赛.php

if(mysqli_num_rows($conleague) > 0)
        {
            echo "<table id = 'legaa' width='100%'>"; 
            while($row = mysqli_fetch_assoc($conleague))
            {
                echo"
                    <tr>
                    <th> <a href = 'teams.php'> ".$row['LeagueName']." </a></th><th>  ".$row['LeagueID']." </th>
                    </tr>";
            }
            echo"</table>";
        }
        $_SESSION["LeagueTeams"] = $row['LeagueName'];
        $_SESSION["LeagueNum"] = $row['LeagueID'];

团队.php

       $leagues = "SELECT team.TeamName, team.TeamID, team.Overall,     team.Budget from teaminfo team WHERE LeagueID = '$_SESSION[LeagueNum]'";
        $conleague = mysqli_query($con,$leagues);
        if(mysqli_num_rows($conleague) > 0)
        {
            echo "<table id = 'legaa' width='100%'>"; 
            while($row = mysqli_fetch_assoc($conleague))
            {
                echo"
                    <tr>
                    <th> <a href = 'showteams.php'> ".$row['TeamName']." </a></th><th>  ".$row['TeamID']." </th> <th> ".$row['Overall']." </th> <th> ".$row['Budget']."</th>
                    </tr>";
            }
            echo"</table>";
        }

我已经设置了两个session_start但它没有打印一些东西：/PS：我的联赛是4个，每个联赛都有一个id（1-4），不应该打印连接到每个联赛ID的球队吗？