By design the client won't return cookies outside of the requested server's domain. Something might be possible with Java script, but I doubt it. This would be a huge security hole.
Now if what you were really asking is if you can get a list of cookies from the client (browser) side, the answer is yes. The cookies are either stored in a file, directory, or the registry (depending on your browser and OS). PHP might not be the best tool for such a task...
