(PHP 3 >= 3.0.13, PHP 4, PHP 5)
posix_getcwd() returns the absolute pathname of the script's current working directory. posix_getcwd() returns FALSE on error.
From the GNU getcwd(3) manpage, paraphrased: returns the absolute pathname of the current working directory. Fails when the current directory is not eradable. Complies with POSIX.1 spec.