How to set a timeout for a sqlsrv_connect() ?

I have in my php.ini:

;extension=php_sqlsrv.dll
;extension=php_sqlsrv_ts.dll
extension=php_sqlsrv_52_ts_vc6.dll

And I'm using IIS 6 on Windows Server 2003.

I'm trying to define a timeout for a sqlsrv_connect() call, but it seems there's no "sqlsrv.connect_timeout" directive that I can set via ini_set(). The script below prints nothing:

<?

print ini_get('sqlsrv.connect_timeout') ;

?>

Thanks for any tips! :)