What are common pitfalls to avoid when handling user input in PHP forms?

One common pitfall to avoid when handling user input in PHP forms is failing to validate and sanitize the input data. This can leave your application vulnerable to security risks such as SQL injection attacks or cross-site scripting. To mitigate this risk, always validate and sanitize user input before using it in your application. 

// Validate and sanitize user input
$username = isset($_POST['username']) ? filter_var($_POST['username'], FILTER_SANITIZE_STRING) : '';
$email = isset($_POST['email']) ? filter_var($_POST['email'], FILTER_VALIDATE_EMAIL) : '';

// Use the sanitized input in your application
// For example, insert into a database
$stmt = $pdo->prepare("INSERT INTO users (username, email) VALUES (:username, :email)");
$stmt->bindParam(':username', $username);
$stmt->bindParam(':email', $email);
$stmt->execute();

Keywords

SQL injection cross-site scripting (XSS) validation htmlspecialchars filter_input

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