我是PHP新手，偶然发现了一个问题。
这是我的代码：
<?php
if (($_GET['marking']) == "Theory") {
?>
<h4 class="mt-0 header-title">Please select month to mark/edit Attendance & Internal Assessment</h4>
<?php
}
else {
?>
<h4 class="mt-0 header-title">Please select month to mark/edit Attendance</h4>
<?php
}
?>
</div>
<div class="row">
<?php
// echo $openclose;
if (isset($_GET['selectedcourseid'])) {
if ($openclose == "internals") {
?>
<a href="markattendanceint.php?selectedsubject=<?=$_GET['selectedsubject'];?>&selectedcourseid=<?=$_GET['selectedcourseid'];?>&type=<?=$_GET['type'];?>&selectedmonth=<?=$acceptmonth?>&marking=<?=$_GET['marking'];?>&teacherid=<?=$userid?>"><button type="button" class="btn btn-danger waves-effect waves-light"><?=$acceptmonth?></button></a>
<?php }
else if ($openclose == "attendance") {
?>
<a href="markattendance.php?selectedsubject=<?=$_GET['selectedsubject'];?>&selectedcourseid=<?=$_GET['selectedcourseid'];?>&type=<?=$_GET['type'];?>&selectedmonth=<?=$acceptmonth?>&marking=<?=$_GET['marking'];?>&teacherid=<?=$userid?>"><button type="button" class="btn btn-danger waves-effect waves-light"><?=$acceptmonth?></button></a>
<?php
}
else if ($openclose == "noresult") {
echo ("Portal closed for your account only. Please contact the AO Office.");
}
else if ($openclose == "close") {
echo ("Portal closed. Please contact the AO Office.");
}
else {
echo ("Bhai tumse na ho payega");
}
}
?>
已将$ openclose设置为用于此情况。但是，无论$ openclose带有什么值，我都无法获得任何输出。没有错误，没有按钮，什么都没有。只是一个空白屏幕。
有人可以帮我吗？
以下是随附的屏幕截图： Blank output
