no php-only solution that i know of... however, depending on what you are actually doing you could always use the 'ln' system call
this will create a virtual link, or virtual directory, every time the file systems accesses you link, it will really be bumped somewhere else
so in this sense you have 'copied' a directory to some other location, you just have not deleted it from the original location
read more at you favorite command prompt:
man ln