php with iis

hi,
i am using php 4.0 with IIS (win 2k). I am using isapi PHP install. I am unable to use

$myBrowser = getenv("HTTP_USER_AGENT");
print $myBrowser;
//i see no output blank screen but no error.

but the following code works

$myBrowser = $_SERVER['HTTP_USER_AGENT'];
print $myBrowser;

can anyone tell me what is that i have to do to make getenv() work. i dont know if i have to do anything with php.ini file. The register_globals value is on and the safe_mode is off. Please let me know what exactly is the problem.

thanks in advance.
ramu

http://nl.php.net/getenv

Note: This function does not work in ISAPI mode.

It probably helps if you search at the php.net website, before asking stupid questions!

thnks jorgen,
thnks for the reply. but your reply was too harsh.
hope you understand that people who are using this forum are sometimes new to php.
bye
ramu