mysql 防注入代码

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

// 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
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->bind_param("ss", $username, $password);

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

// 获取结果
$result = $stmt->get_result();

// 处理结果
if ($result->num_rows > 0) {
    echo "登录成功";
} else {
    echo "登录失败";
}

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