$value) { echo "$name: $value\n"; } ?>
This code checks if the HTTP_REFERER header is set in the request and if it contains the word 'facebook.com'. If it does, the code performs a specific action for Facebook traffic. If it doesn't, the code performs a different action for all other traffic. Both of these examples use PHP's built-in functions to access and work with headers sent in an HTTP request. The package library used is native PHP, which provides a variety of functions and methods for handling HTTP requests.