PHP数据库连接安全性：防止SQL注入攻击的方法

// 数据库连接参数
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";

// 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);
}

// 使用预处理语句进行查询
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->bind_param("ss", $username, $password);

// 设置查询参数
$username = $_POST['username'];
$password = $_POST['password'];

// 执行查询
$stmt->execute();

// 处理查询结果
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    // 处理每一行的数据
}

// 关闭连接
$stmt->close();
$conn->close();

// 数据库连接参数
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";

// 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);
}

// 准备查询语句
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ? AND password = ?");

// 绑定查询参数
$stmt->bind_param("ss", $_POST['username'], $_POST['password']);

// 执行查询
$stmt->execute();

// 处理查询结果
$result = $stmt->get_result();
while ($row = $result->fetch_assoc()) {
    // 处理每一行的数据
}

// 关闭连接
$stmt->close();
$conn->close();

// 数据库连接参数
$servername = "localhost";
$username = "root";
$password = "password";
$dbname = "mydb";

// 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);
}

// 过滤输入的字符串
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

// 执行查询
$sql = "SELECT * FROM users WHERE username = '$username' AND password = '$password'";
$result = $conn->query($sql);

// 处理查询结果
if ($result->num_rows > 0) {
    while ($row = $result->fetch_assoc()) {
        // 处理每一行的数据
    }
} else {
    echo "0 结果";
}

// 关闭连接
$conn->close();