我在这里遇到问题。首先,我在这里做的是学生的学科注册系统。我设置了一部分代码来限制同一个学生一次又一次地注册同一个主题。但令人遗憾的是,这给了我一个相反的效果。我的错误是,当一个学生注册一个科目时,即使他们从未注册过该科目,其他学生也不能注册该特定科目。任何帮助将非常感激。主题注册错误
<?php
if(!isset($_POST['submit'])){
exit('Unauthorized access!');
}
$name = $_POST['name'];
$studentid = $_POST['studentid'];
$program = $_POST['program'];
$fintake = $_POST['fintake'];
$courseid = $_POST['courseid'];
include("include/config.php");
//this could be the problem,i'm not sure
$check_query = mysqli_query($link, "SELECT r_id FROM course_registration WHERE r_cid='$courseid' limit 1");
if(mysqli_fetch_array($check_query))
{
echo 'Error:Course ID:',$courseid,' already exists. <a href="javascript:history.back(-1);">Return</a>';
exit;
}
$result = mysqli_query($link, "SELECT * FROM course_list WHERE c_cid = '$courseid'");
if(mysqli_fetch_array($result))
{
$sql = "INSERT INTO course_registration (r_name,r_sid,r_program,r_fintake,r_cid) VALUES('$name','$studentid','$program','$fintake','$courseid')";
if(mysqli_query($link,$sql))
{
exit('Success! Register course successfully. <a href="index.php">Homepage</a>');
}
else
{
echo 'Sorry! Add data failed:',mysqli_error($link),'<br />';
echo 'Click here <a href="javascript:history.back(-1);">Return</a> retry';
}
}
else
{
echo 'Sorry! Wrong course id.','<br />';
echo 'Click here <a href="javascript:history.back(-1);">Return</a> retry';
}
?>
数据库:course_registration
r_id r_name r_sid r_program r_fintake r_cid
1 TAN KOON ENG 0187904 DIP-CS 01-2015 DTP-3033
2 TAN KOON ENG 0187904 DIP-CS 01-2015 DCS-22104
3 CRISTIANO RONALDO 0190007 DIP-GT 09-2016 DGP-2254
4 CRISTIANO RONALDO 0190007 DIP-GT 09-2016 DGA-1224
add where clause studentid = $ studenid。 – JYoThI