Getting a unique id from headers

[RamiX]

Hi,
i want to identify my site visitor from the data that is sent on the headers.
i read that there's a header called HTTP_X_UP_SUBNO that gives kind of an id.
i followed the data that sent from users but few of them had data there (HTTP_X_UP_SUBNO).
my question, actualy few questions.
1. is this HTTP_X_UP_SUBNO belongs to the telephone or to the sim card?
2. is there any way to get this code for all users ?
3. is there any way to get data about the sim (like phone number)?

thanks all

[petrib]

The web site will only get the phone number (MSISDN) if the network operator (carrier, service provider) adds it to HTTP headers. Most operators will not add it. Some will add it only for traffic going through their WAP access point. Some will add it, but only if you pay them.

And with 1000+ network operators that people could happen to use to get to your web site using their phones, and the varying practices of those operators, you can forget about getting the MSISDN.

Your only semi-reliable way to uniquely identify the users is to do what everybody does: set a cookie, or ask them to register and use a username/password.