With every cookie created, there is the name of it, what is stored inside, the expiration time, the path it can be read from, the domain it can be read from, and a secure flag. If the cookie written by apache specifies that it can not be read by the domain or directory you are looking at it from, you cant read it.
$HTTP_COOKIE is an array containing all of the cookies that can be read from wherever it is called. Run the phpinfo() again and under Apache Environment, look for HTTP_COOKIE and see what it prints out for available cookies.
-Chris