mysqli 预处理

<?php
$servername = "localhost";
$username = "your_username";
$password = "your_password";
$dbname = "your_database";

// 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);
}

// 准备 SQL 语句
$stmt = $conn->prepare("SELECT id FROM users WHERE username = ? AND password = ?");

// 绑定参数
$stmt->bind_param("ss", $username, $password);

// 设置参数并执行
$username = $_POST['username'];
$password = $_POST['password'];
$stmt->execute();

// 绑定结果变量
$stmt->bind_result($id);

// 获取结果
if ($stmt->fetch()) {
    echo "登录成功，用户 ID: " . $id;
} else {
    echo "登录失败";
}

// 关闭语句和连接
$stmt->close();
$conn->close();
?>