Description:
------------
Folloing code returns false when decrypting originally empty 
string:

        $gpg = new gnupg();
        $gpg->adddecryptkey($fingerprint, $passphrase);
        $output = $gpg->decrypt($data);

$output will be false, but $gpg->geterror() returns false 
also, so you can check that no error has happened. Output 
should be empty string?.