phpmysql登录代码

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "database_name";

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

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

// 预处理语句防止SQL注入
$stmt = $conn->prepare("SELECT id FROM users WHERE username=? AND password=?");
$stmt->bind_param("ss", $username, $password);

$username = $_POST['username'];
$password = $_POST['password']; // 注意：实际应用中应使用密码哈希

$stmt->execute();
$stmt->store_result();

if ($stmt->num_rows == 1) {
    echo "登录成功";
} else {
    echo "用户名或密码错误";
}

$stmt->close();
$conn->close();
?>