PHP开发实时聊天系统的用户签名和个人资料设置

CREATE TABLE `users` (
  `id` int(11) UNSIGNED AUTO_INCREMENT PRIMARY KEY,
  `username` varchar(50) NOT NULL,
  `password` varchar(255) NOT NULL,
  `email` varchar(50) NOT NULL,
  `signature` varchar(100) DEFAULT NULL,
  `profile_pic` varchar(255) DEFAULT NULL,
  `created_at` timestamp NOT NULL DEFAULT current_timestamp(),
  `updated_at` timestamp NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp()
);

<form action="profile_update.php" method="POST">
  <label>用户名：</label>
  <input type="text" name="username" value="<?php echo $username; ?>" required>
  <br>
  <label>邮箱：</label>
  <input type="email" name="email" value="<?php echo $email; ?>" required>
  <br>
  <label>个性签名：</label>
  <textarea name="signature"><?php echo $signature; ?></textarea>
  <br>
  <label>头像：</label>
  <input type="file" name="profile_pic">
  <br>
  <input type="submit" value="保存">
</form>

<?php
// 连接数据库
$db = new mysqli('localhost', 'username', 'password', 'database_name');

// 检查连接是否成功
if ($db->connect_errno) {
  die('连接数据库失败：' . $db->connect_error);
}

// 获取用户提交的信息
$username = $_POST['username'];
$email = $_POST['email'];
$signature = $_POST['signature'];
$profile_pic = $_FILES['profile_pic']['name'];
$tmp_name = $_FILES['profile_pic']['tmp_name'];

// 保存用户信息到数据库
$sql = "UPDATE `users` SET `username`='$username', `email`='$email', `signature`='$signature', `profile_pic`='$profile_pic' WHERE `id` = $user_id";
if ($db->query($sql) === TRUE) {
  echo "用户信息已保存";
} else {
  echo "保存失败：" . $db->error;
}

// 保存用户头像到服务器
move_uploaded_file($tmp_name, 'profile_pics/' . $profile_pic);

// 关闭数据库连接
$db->close();