What is the recommended method for filtering and validating form input in PHP?

When dealing with form input in PHP, it is important to filter and validate the data to prevent security vulnerabilities such as SQL injection and cross-site scripting attacks. The recommended method for filtering and validating form input in PHP is to use filter_input() function along with filter_var() function to sanitize and validate the input data.

// Filter and validate form input
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$email = filter_input(INPUT_POST, 'email', FILTER_VALIDATE_EMAIL);

if (!$username || !$email) {
    // Handle invalid input
    echo "Invalid input. Please try again.";
} else {
    // Process the input data
    echo "Username: " . $username . "<br>";
    echo "Email: " . $email;
}