Apache

When defining a SSL virtual host this way:

<VirtualHost *:443>
        DocumentRoot "/your/document/root"
        ServerName your.domain.name
</VirtualHost>

the HTTPS environment variable is not set, hence, for example, the $_SERVER['HTTPS'] is not set under PHP, leading to errors, especially for a service which is only available through HTTPS.

You normally had to add SSLOptions +StdEnvVars entry in the Apache configuration file, but, due to some restrictions concerning SSL, you have apparently also to set most of the SSL related directives.