php 防止mysql注入

<?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 = ?");
$stmt->bind_param("s", $username);

$username = $_POST['username'];

$stmt->execute();

$result = $stmt->get_result();

while ($row = $result->fetch_assoc()) {
    echo "id: " . $row["id"]. " - Name: " . $row["username"]. "<br>";
}

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

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

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    // 设置 PDO 错误模式为异常
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 预处理语句
    $stmt = $conn->prepare("SELECT * FROM users WHERE username = :username");
    $stmt->bindParam(':username', $username);

    $username = $_POST['username'];

    $stmt->execute();

    $result = $stmt->fetchAll();

    foreach ($result as $row) {
        echo "id: " . $row["id"]. " - Name: " . $row["username"]. "<br>";
    }
} catch(PDOException $e) {
    echo "连接失败: " . $e->getMessage();
}

$conn = null;
?>