REQUEST_URI and URL Anchors

How to retrieve the anchor value: page.html#bottom

[geckofuel]

I'd like to be able to find the anchor value of URLs but am having trouble finding a way to do this in PHP. Any suggestions?

for example if the following page is accessed:

page.html#bottom

REQUEST_URI only returns page.html. How would I retrieve the #bottom portion?

[DrDoc]

PHP Predefined Variables [php.net]

Tried QUERY_STRING?

[eaden]

[php.net...]

[DrDoc]

...or $_GET[0]?