php mysql不能自动反转义

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

try {
    $conn = new PDO("mysql:host=$servername;dbname=$dbname", $username, $password);
    $conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);

    // 预处理语句
    $stmt = $conn->prepare("INSERT INTO users (username, email) VALUES (:username, :email)");
    $stmt->bindParam(':username', $username);
    $stmt->bindParam(':email', $email);

    $username = "JohnDoe";
    $email = "john@example.com";

    $stmt->execute();

    echo "New record created successfully";
} catch(PDOException $e) {
    echo "Error: " . $e->getMessage();
}

$conn = null;
?>