i was under the impression mkdir() could only make 1 directory per call.
so as long as the pictures/ dir is already created, then pic/ should be created inside of it(assuming pictures/ is writable)
if safemode is on, and you try to do this
mkdir ("pictures", 0700);
mkdir ("pictures/pic", 0700);
i dont think its going to work. i beleive in safemode when directories are created, they are not created by the same uid as php. so trying to create a sub directory in a directory created w/ mkdir isnt possible under safemode