help condensing regular expressions

Hi I am trying to calculate how far into a directory structure I am so that I can include images and include files without having to hard code them. I need to turn $PHP_SELF which could be /admin/emails/index.php into ../../ which I can then use to get to any directory from root. like IMG src=<?echo $relative_root?>images/logo.png Regular expressions leave me cold but I have come up with the following monster which works $relative_root = preg_replace("<\/[[:alnum:]]+>","../", preg_replace("</[[:alnum:]]+$>","",strtok($PHP_SELF,"."))); Anybody have a better solution? Thanks for any help. Tom