如何使用PHP开发简单的在线学习平台和课程管理功能

//连接数据库
$connection = mysqli_connect('localhost', 'username', 'password', 'database_name');

//用户注册
if(isset($_POST['register'])) {
  $username = $_POST['username'];
  $password = $_POST['password'];
  
  //检查用户名是否已经存在
  $query = "SELECT * FROM users WHERE username='$username'";
  $result = mysqli_query($connection, $query);
  if(mysqli_num_rows($result) > 0) {
    echo "用户名已经存在，请重新选择用户名！";
  } else {
    //插入新用户到数据库中
    $query = "INSERT INTO users (username, password) VALUES ('$username', '$password')";
    mysqli_query($connection, $query);
    echo "注册成功！";
  }
}

//用户登录
if(isset($_POST['login'])) {
  $username = $_POST['username'];
  $password = $_POST['password'];
  
  //检查用户名和密码是否匹配
  $query = "SELECT * FROM users WHERE username='$username' AND password='$password'";
  $result = mysqli_query($connection, $query);
  if(mysqli_num_rows($result) > 0) {
    echo "登录成功！";
  } else {
    echo "用户名或密码错误，请重新输入！";
  }
}

//关闭数据库连接
mysqli_close($connection);

//连接数据库
$connection = mysqli_connect('localhost', 'username', 'password', 'database_name');

//创建课程
if(isset($_POST['create_course'])) {
  $course_name = $_POST['course_name'];
  $teacher_id = $_POST['teacher_id'];
  
  //插入新课程到数据库中
  $query = "INSERT INTO courses (course_name, teacher_id) VALUES ('$course_name', '$teacher_id')";
  mysqli_query($connection, $query);
  echo "课程创建成功！";
}

//编辑课程
if(isset($_POST['edit_course'])) {
  $course_id = $_POST['course_id'];
  $new_course_name = $_POST['new_course_name'];
  
  //更新课程名称
  $query = "UPDATE courses SET course_name='$new_course_name' WHERE course_id='$course_id'";
  mysqli_query($connection, $query);
  echo "课程编辑成功！";
}

//删除课程
if(isset($_POST['delete_course'])) {
  $course_id = $_POST['course_id'];
  
  //删除课程
  $query = "DELETE FROM courses WHERE course_id='$course_id'";
  mysqli_query($connection, $query);
  echo "课程删除成功！";
}

//浏览课程列表
$query = "SELECT * FROM courses";
$result = mysqli_query($connection, $query);
while($row = mysqli_fetch_assoc($result)) {
  echo $row['course_id'].": ".$row['course_name']."<br>";
}

//关闭数据库连接
mysqli_close($connection);