Need to get document url in PHP

[MAC]

I'm trying to include PHP files as the header and footer of my web pages. The output of the PHP file needs to change slightly based on what directory in my website the document with the header and footer is in.
Is there any environmental variable like DOCUMENT_URL in PHP, so that I can find out what url the browser is requsting?

Thanks!

[MAC]

I just found out how! The var is $REQUEST_URI

[RAGE]

I prefer using $PHP_SELF ...

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