$name = "JohnDoe"; if (ctype_alpha($name)) { echo "Valid name!"; } else { echo "Invalid name."; }
$email = "johndoe@example.com"; if (filter_var($email, FILTER_VALIDATE_EMAIL)) { echo "Valid email address!"; } else { echo "Invalid email address."; }This code checks if the string `$email` is a valid email address using the `FILTER_VALIDATE_EMAIL` filter, and if it is, it prints "Valid email address!" on the screen. In terms of package libraries, there are many PHP libraries available for validating strings, such as Respect\Validation, which provides a collection of validation rules for various data types including strings. Other popular validation libraries for PHP include Symfony Validator and Laravel Validator.