> mkdir a
> ln -s a b
> touch a/t
> perl -e ' print "yes\n" if (-e "a/t");'
yes
> perl -e ' print "yes\n" if (-e "b/t");'
yes
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As you can see, in general it works. Are you sure you have the right path? Web address and filesystem path of any file can be totally different because of apaches ability to rewrite addresses

Did you check if you can test whether the directory exists? Or its parent directory and so on?