What potential pitfalls should be avoided when allowing users to register themselves in a PHP community site?

One potential pitfall to avoid when allowing users to register themselves in a PHP community site is not properly validating user input. This can leave the site vulnerable to SQL injection attacks or other security threats. To prevent this, always sanitize and validate user input before using it in database queries or other operations. 

// Validate and sanitize user input before using it
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);
$password = password_hash($_POST['password'], PASSWORD_DEFAULT);

// Then use the sanitized input in your database query or other operations
$stmt = $pdo->prepare("INSERT INTO users (username, email, password) VALUES (:username, :email, :password)");
$stmt->bindParam(':username', $username);
$stmt->bindParam(':email', $email);
$stmt->bindParam(':password', $password);
$stmt->execute();

Keywords

SQL injection cross-site scripting password hashing CSRF protection user input validation

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