我正在做作业。我只需要在选中复选框时使用jquery显示按钮，并且只针对少数主题。所有主题都来自使用php和mysql的后端。表正在动态获取主题。
我想显示按钮或文本时，只有少数科目被选中
这是密码

<?php
if($stmt = $conn->prepare("SELECT classid, code, name, teacher, classroom, 
time, cost FROM classes ORDER BY classid")){
    // $stmt->bind_param("isssssd");
    $result = $stmt->execute();
    $stmt->bind_result($classid, $code, $name, $teacher, $classroom, $time, 
$cost);

    $checked = "";
    while ($stmt->fetch()) {
$row = array("classid"=>$classid, "code"=>$code, "name"=>$name, 
"teacher"=>$teacher, "classroom"=>$classroom, "time"=>$time, "cost"=>$cost);
        if(in_array($classid, $selectedclasses)){
            $checked = "checked";
        }else{
            $checked = "";
        }

    ?>

    <div class="row col-md-12">
        <hr/>
    </div>

    <div class="row col-md-12" id="class_<?php echo $classid; ?>">
        <div class="col-md-4 col-lg-4 col-sm-6 col-sx-6">
<input type="checkbox" id="classitem_<?php echo $classid; ?>" 
name="classitem_<?php echo $classid; ?>" class="classitem" value="<?php echo 
$classid; ?>" <?php echo $checked; ?> > <?php echo $name; ?>
        </div>
        <div class="col-md-2 col-lg-2 col-sm-6 col-sx-6">
<?php echo $teacher; ?>
        </div>
        <div class="col-md-2 col-lg-2 col-sm-6 col-sx-6">
<?php echo $cost; ?>
        </div>
        <div id="mine" class="col-md-4 col-lg-4 col-sm-6 col-sx-6">
<?php echo $time; ?>
        </div>
    </div>

    <?php
    }

    $stmt->close();
}
    ?>