php怎么更改数据表的字段类型

// 连接数据库
$servername = "localhost";
$username = "username";
$passWord = "password";
$dbname = "database";

// 创建连接
$conn = new mysqli($servername, $username, $password, $dbname);

// 检查连接是否成功
if ($conn->connect_error) {
   die("连接失败: " . $conn->connect_error);
}

// 获取数据表结构
$sql = "DESC users";
$result = $conn->query($sql);

// 更改字段类型
$sql = "ALTER TABLE users MODIFY age VARCHAR(50)";
if ($conn->query($sql) === TRUE) {
   echo "字段类型已更改";
} else {
   echo "更改字段类型失败：" . $conn->error;
}

// 添加新的字段
$sql = "ALTER TABLE users ADD address VARCHAR(100)";
if ($conn->query($sql) === TRUE) {
   echo "新的字段已添加";
} else {
   echo "添加新的字段失败：" . $conn->error;
}

// 关闭连接
$conn->close();