...thanks, I should have been more specific - how can I access referrer url field from the extension code? I realize it might be more of a php question rather then MW.

kind of expected this to be put into $wgRequest object since referrer is part of the HTTP request header, but I couldn't find it there.

Which hook can I use for the following? (in the case it looks reasonable)

$wgHooks['somehook'][] = 'run_greeting'; function run_greeting(){ $msg = function_of(somehow_get_referrer_url()); $wgOut->prependHTML($my_message); }

Thank you!

Evgeny.