PHPで従業員の休暇管理機能を実装するにはどうすればよいですか?

<form method="post" action="process_leave.php">
  <label for="employee_name">员工姓名:</label>
  <input type="text" name="employee_name" id="employee_name" required>
  
  <label for="leave_type">请假类型:</label>
  <select name="leave_type" id="leave_type" required>
    <option value="病假">病假</option>
    <option value="事假">事假</option>
    <option value="年假">年假</option>
  </select>
  
  <label for="leave_start_date">请假开始日期:</label>
  <input type="date" name="leave_start_date" id="leave_start_date" required>
  
  <label for="leave_end_date">请假结束日期:</label>
  <input type="date" name="leave_end_date" id="leave_end_date" required>
  
  <label for="leave_reason">请假原因:</label>
  <textarea name="leave_reason" id="leave_reason" required></textarea>
  
  <input type="submit" value="提交申请">
</form>

<?php
// 连接到数据库
$conn = mysqli_connect("localhost", "root", "password", "leave_management");

// 检查连接是否成功
if (!$conn) {
  die("数据库连接失败: " . mysqli_connect_error());
}

// 获取表单中的字段值
$employee_name = $_POST['employee_name'];
$leave_type = $_POST['leave_type'];
$leave_start_date = $_POST['leave_start_date'];
$leave_end_date = $_POST['leave_end_date'];
$leave_reason = $_POST['leave_reason'];

// 编写SQL语句并执行插入操作
$sql = "INSERT INTO leave_requests (employee_name, leave_type, leave_start_date, leave_end_date, leave_reason, status) 
        VALUES ('$employee_name', '$leave_type', '$leave_start_date', '$leave_end_date', '$leave_reason', '待审批')";

if (mysqli_query($conn, $sql)) {
  echo "请假申请提交成功";
} else {
  echo "请假申请提交失败: " . mysqli_error($conn);
}

// 关闭数据库连接
mysqli_close($conn);
?>

<?php
// 连接到数据库
$conn = mysqli_connect("localhost", "root", "password", "leave_management");

// 检查连接是否成功
if (!$conn) {
  die("数据库连接失败: " . mysqli_connect_error());
}

// 查询请假信息
$sql = "SELECT * FROM leave_requests";
$result = mysqli_query($conn, $sql);

if (mysqli_num_rows($result) > 0) {
  while ($row = mysqli_fetch_assoc($result)) {
    echo "员工姓名: " . $row['employee_name'] . "<br>";
    echo "请假类型: " . $row['leave_type'] . "<br>";
    echo "请假开始日期: " . $row['leave_start_date'] . "<br>";
    echo "请假结束日期: " . $row['leave_end_date'] . "<br>";
    echo "请假原因: " . $row['leave_reason'] . "<br>";
    echo "请假状态: " . $row['status'] . "<br><br>";
  }
} else {
  echo "暂无请假申请";
}

// 关闭数据库连接
mysqli_close($conn);
?>