我的目标:一旦按下按钮,就无法再次按下。它应该给出错误或某种消息,例如(当第一次按下按钮以标记出勤并且有人再次按下它时)
"已标记出勤,您不能再次标记您的出勤"
<?php
session_start();
?>
<form method="post">
<button name="attendence" >mark attendence </button>
</form>
<?php
if (isset($_POST['attendence'])){
$id =$_SESSION["id"];
$con = mysqli_connect('localhost','root','','yo');
$query = "INSERT INTO attendance (present,absent, datetime, std_id) VALUES ('present','',current_timestamp(), $id ) ";
$rs=mysqli_query($con,$query);
if($rs){
echo "Marked as Present";
}
else {
echo "marked as Absent";
}
}