Passing values containing a ? and a &

I want to assign a value using the url however the value contains both a ? and an & so PHP (or the browser) seems to get confused. Here's an example: http://www.mysite.com/index.php?id=23&url=http://www.anothersite.com/file.ph p?qid=234&forum=4 Everything after url= should be the value of $url but this is not the case. Is there a way to solve this? Thanks