html代码连接mysql数据库

<form action="query.php" method="post">
  <label for="host">Host:</label>
  <input type="text" id="host" name="host"><br><br>
  <label for="username">Username:</label>
  <input type="text" id="username" name="username"><br><br>
  <label for="password">Password:</label>
  <input type="password" id="password" name="password"><br><br>
  <input type="submit" value="Connect">
</form>

<?php
$host = $_POST['host'];
$username = $_POST['username'];
$password = $_POST['password'];

// 连接MySQL数据库
$conn = mysqli_connect($host, $username, $password);
if (!$conn) {
  die('数据库连接失败: ' . mysqli_connect_error());
}

// 执行查询操作
$sql = "SELECT * FROM table_name";
$result = mysqli_query($conn, $sql);

// 处理查询结果
if (mysqli_num_rows($result) > 0) {
  while ($row = mysqli_fetch_assoc($result)) {
    echo "字段1: " . $row["column1"]. " - 字段2: " . $row["column2"]. "<br>";
  }
} else {
  echo "没有查询到结果";
}

// 关闭数据库连接
mysqli_close($conn);
?>