如何使用PHP实现微信小程序的自动签到功能？

CREATE TABLE `sign_records` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `user_id` int(11) NOT NULL,
  `sign_time` datetime NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

<?php
// 连接数据库
$servername = "localhost";
$username = "root";
$passWord = "";
$dbname = "test";

$conn = mysqli_connect($servername, $username, $password, $dbname);

if (!$conn) {
    die("连接失败: " . mysqli_connect_error());
}

header('Content-Type: application/json');

$user_id = $_POST['user_id'];

$sql = "INSERT INTO sign_records (user_id, sign_time) VALUES ('$user_id', NOW())";
$result = mysqli_query($conn, $sql);

if ($result) {
    $response['status'] = 'success';
    $response['message'] = '签到成功';
} else {
    $response['status'] = 'error';
    $response['message'] = '签到失败';
}

echo json_encode($response);

wx.request({
  url: 'Http://example.com/checkin.php',
  method: 'POST',
  data: {
    user_id: 123 // 用户ID需要根据实际情况来传递
  },
  success: function (res) {
    if (res.data.status === 'success') {
      // 签到成功的处理逻辑
    } else {
      // 签到失败的处理逻辑
    }
  },
  fail: function (res) {
    // 请求失败的处理逻辑
  }
})