php怎么登录mysql数据库

<?php
$servername = "localhost"; // MySQL服务器地址
$username = "your_username"; // MySQL用户名
$password = "your_password"; // MySQL密码
$dbname = "your_database"; // 数据库名称

// 创建数据库连接
$conn = new mysqli($servername, $username, $password, $dbname);

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

// 进行登录操作
$sql = "SELECT * FROM users WHERE username='your_username' AND password='your_password'";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
    // 登录成功
    echo "登录成功";
} else {
    // 登录失败
    echo "用户名或密码错误";
}

// 关闭数据库连接
$conn->close();
?>