What are some common pitfalls to avoid when handling user input and processing form data in PHP?

One common pitfall to avoid when handling user input and processing form data in PHP is not properly sanitizing and validating user input. This can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To prevent this, always sanitize and validate user input before using it in your application. 

// Sanitize and validate user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_VALIDATE_EMAIL);

// Example of using sanitized input
$query = "SELECT * FROM users WHERE username = '$username' AND email = '$email'";

Keywords

SQL injection cross-site scripting validation sanitization escaping

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