Yep, just finished mine up yesterday, actually, and had similar PATH_INFO issues, perhaps. If you're on Ubuntu using FPM, here's what I did:
1. Added this line to my fastcgi_params file
fastcgi_param PATH_INFO $fastcgi_path_info;
2. In my authenticating virtual host (not the IDP host), I added
location ~ ^/simplesaml/(.+\.php.*)$ {
alias /opt/dev/saml-sp/www/$1;
# The usual fastcgi stuff plus...
fastcgi_split_path_info ^(.+\/module\.php)(/.+)$;
}
location ~ ^/simplesaml/(.*) {
alias /opt/dev/saml-sp/www/$1;
}
Hope that helps. It's not fully tested yet, but seems okay so far.