This function seems to be very slow on IIS 4.0 Server (Win32). I use system call to NSLOOKUP instead to get PC-Hostname:
unset ($execoutput);
exec ("nslookup $IPAdresse 2>nul",$execoutput,$nslookstatus);
if (isset ($execoutput[3]) && ereg ("^Name: *([A-Za-z0-9]{2,})\.",$execoutput[3],$regs))
$nslookname=strtoupper($regs[1]);
else $nslookname="Unknown";
Note by members: This is not portable to Windows platforms. so you would be better to stay with our function.