What are the potential pitfalls of not using proper PHP syntax in form processing?

Not using proper PHP syntax in form processing can lead to errors in data validation, sanitization, and processing, potentially leaving the application vulnerable to security threats such as SQL injection or cross-site scripting attacks. To avoid these pitfalls, it is crucial to follow best practices for form processing, including using functions like htmlspecialchars() for sanitizing user input and prepared statements for database queries. 

// Example of using proper PHP syntax for form processing
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = htmlspecialchars($_POST["username"]);
    $password = htmlspecialchars($_POST["password"]);

    // Use prepared statements to prevent SQL injection
    $stmt = $pdo->prepare("SELECT * FROM users WHERE username = ?");
    $stmt->execute([$username]);
    $user = $stmt->fetch();

    // Validate user input and process form data
    if ($user && password_verify($password, $user['password'])) {
        // User authentication successful
    } else {
        // User authentication failed
    }
}

Keywords

syntax error form processing security vulnerability data validation error handling

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