PHP troubles

Are there any predefined variables in php that display the directory that the script is currently being run? The first directory; I mean, not the full path since the doccument root.

If not, is there any way to work around it/remove certain text from a string?

1  get full path from $_SERVER['PHP_SELF']
2  split it using EXPLODE into array
3  get whichever item of array you want
4  profit

but maybe i have misunderstood it..