Location regular expression explanation

[diego_xa]

Hi,

I was recently reading the PHPfastcgi example at
http://wiki.nginx.org/PHPFcgiExample. When it talks about the
configuration to avoid the exploit on uploads folder, there is a
regulare expresion saying: location ~*
(^(?!(?:(?!(php|inc)).)*/blogs\.dir/).*?(php|inc)) {

I don't understand that regular expresion. Could someone explain me what
?! ?: mean or send me some link to documentation about this?? I cannot
find anything after some googling.

Thanks and regards.

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,229276,229276#msg-229276