[OpenSER-Users] Hints about to capture codes negative www_authorize??

Hi, Who would have tips on how to capture the return codes negative of the function "www_authorize" ??? I read somewhere that said to use $retval........but ...How can I to use it ("$retval") ?? -1 - Non existent user; -2 - invalid passwd; -3 - stale nonce; -4 - no credentials; -5 - error; Any help will be greatly appreciated. thx, Marcio