I've been struggling for a while with a strange bug that I'd like to share. I had two web applications protected with an apache module called mod-auth-openid, which provides an authentication using openid. Here is the sequence diagram for one authentication :

It might seem trivial to retrieve boolean settings from php's configuration with the use of ini_get(). As an example, we will try to know if php is running in safe_mode or not. There is a ini directive for this, which can be defined in php.ini or in httpd.conf .

in php.ini :

safe_mode = 0

in httpd.conf :

php_admin_value safe_mode 0

Now, let's try to guess its value from a php script.