Converting IP Addresses and Hostnames
Even if your server does not provide you with a $_SERVER['REMOTE_HOST'] variable, you will probably know the IP address of a visitor from the $_SERVER['REMOTE_ADDR'] environment variable. You can use this in conjunction with the function gethostbyaddr() to get the user’s hostname. gethostbyaddr() requires a string representing an IP address and returns the equivalent hostname. If an error occurs, it returns the IP address it was given. Listing 14.5 creates a script that uses gethostbyaddr() to acquire the user’s hostname if the $REMOTE_HOST variable is unavailable.
Listing 14.5. Using gethostbyaddr() to Get a Hostname
1: <!DOCTYPE html PUBLIC 2: "-//W3C//DTD XHTML 1.0 Strict//EN" 3: "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> ... |
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