My php script called from my extensions.conf is working fine, however 
each time I run it with agi debug mode on I see the message
AGI Rx << Done
AGI Tx >> 510 Invalid or unknown command
which does not come from my script, apart from the Rx << Done where the 
'Done' is the message from my exit() statement.
If I omit the exit() statement I get
AGI Rx <<
AGI Tx >> 510 Invalid or unknown command
AGI Rx <<
AGI Tx >> 510 Invalid or unknown command
output after the last transmission to STDERR.
It appears to be cosmetic, just wondering if I have anything to be 
concerned about here?
-- 
Colin Beckingham
(613) 374-1391
Skype: it4gh_
http://www.it4gh.com