$email = "example@email.com"; if (filter_var($email, FILTER_VALIDATE_EMAIL)) { echo "Email is valid"; } else { echo "Email is not valid"; }
$username = "example_123"; if (preg_match('/^[a-zA-Z0-9_]+$/', $username)) { echo "Username is valid"; } else { echo "Username is not valid"; }These validation functions are included in the core PHP package and do not require an external library.