$url = "http://example.com";
$url = "http://example.com/search?q=term&page=1";
$url = "http://example.com#section-1";This code defines a URL with a fragment identifier "section-1". These examples use the built-in PHP functions to manipulate URL components, such as parse_url(), parse_str(), and http_build_query(). The package library used here is the PHP Standard Library. In addition, there are various PHP libraries and frameworks specifically designed for handling URLs and routing, such as Symfony Routing, Laravel Routing, and Slim Framework. These libraries provide more advanced features and functionality for working with URLs in PHP.