Example :
I go in the browser at :
www.example.com/documents/pages/doc.php?bacon=baked&this=tastes_good
And I would like that this link access to this page with the path encoded into the query :
www.example.com/index.php?url=documents%2Fpages%2Fdoc.php%3Fbacon%3Dbaked%26this%3Dtastes_good
The thing is that this index.php will need to take the big "url" query variable to decode and modify it in PHP and then fopen() the wanted page from an other site.
I need to do all that because the two sites need to use the same $_SESSION, databases and files and it would be harder to completely separate.