如何用PHP开发微信小程序的运动课程预订功能？

// 连接数据库
$servername = "localhost";
$username = "root";
$passWord = "123456";
$dbname = "test";
$conn = new mysqli($servername, $username, $password, $dbname);

// 获取运动课程列表
$sql = "SELECT * FROM courses";
$result = $conn->query($sql);
$courses = array();
if ($result->num_rows > 0) {
  while($row = $result->fetch_assoc()) {
    $courses[] = $row;
  }
}

// 用户预订课程
$userID = $_POST['userID'];
$courseID = $_POST['courseID'];

// 验证用户ID和课程ID的有效性，此处省略验证逻辑
// ...

// 将预订信息插入到数据库
$sql = "INSERT INTO orders (userID, courseID, orderTime) VALUES ('$userID', '$courseID', NOW())";
if ($conn->query($sql) === TRUE) {
  // 更新"courses"表格中的剩余名额字段
  $sql = "UPDATE courses SET remaining_slots = remaining_slots - 1 WHERE courseID = '$courseID'";
  $conn->query($sql);

  echo "预订成功！";
} else {
  echo "预订失败！";
}

// 关闭数据库连接
$conn->close();