$name = "John Doe"; if (strlen($name) > 50) { echo "Name is too long"; } else { echo "Name is valid"; }This example checks if the length of the $name string is greater than 50 characters. If it is, it will output "Name is too long". If not, it will output "Name is valid". The package library used in this example is the PHP core library. However, there are many other third-party libraries and frameworks available in PHP that provide additional string validation functions and tools. Some popular examples include the Symfony Validator component, Laravel Validation package, and the Zend Validator class.