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<?php

//
//  <string> remote_ip( )
//
//  Returns the IP address(s) of the remote user
//  

function remote_ip( )
{
	$keys = array
	(
		"HTTP_CLIENT_IP",
		"HTTP_X_FORWARDED_FOR",
		"HTTP_X_FORWARDED",
		"HTTP_FORWARDED_FOR",
		"HTTP_FORWARDED",
		"REMOTE_ADDR",
	);

	$list = array
	(
		true  => array(),
		false => array(),
	);
		
	foreach ($keys as $key)
		if (isset($_SERVER[$key]) && is_string($_SERVER[$key]))
			foreach (explode(",", $_SERVER[$key]) as $ip)
				if (is_ipv4($ip = trim($ip)))
					$list[is_local_ipv4($ip)][] = $ip;

	list($local, $remote) = array_values($list);

	usort($remote, "ipcmp");
	usort($local,  "ipcmp");

	return implode(",", array_merge($remote, $local));
}		

//
//  <boolean> is_ipv4( <string> $ip )
//
//  Returns TRUE if the passed string is an IPv4 address
//

function is_ipv4( $ip )
{
	if (!preg_match("`^d+(.d+){3}$`ims", $ip))
		return false;

	foreach (explode(".", $ip) as $part)
		if ($part > 255)
			return false;

	return true;
}

//
//  <boolean> is_local_ipv4( <string> $ip )
//
//  Returns TRUE if the passed IPv4 address is local (see RFC 1918)
//

function is_local_ipv4( $ip )
{
	$table = array
	(
		  167772160 => 4278190080,	// (127/8)
		 2130706432 => 4278190080,	// (10/8)
		 2886729728 => 4293918720,	// (172.16/12)
		 3232235520 => 4294901760,	// (196.168/16)
	);

	$net = iptolong($ip);

	foreach ($table as $addr => $mask)
		if (($net & $mask) == $addr)
			return true;
		
	return false;
}

//
//  <integer> iptolong( <string> $ip )
//
//  Replacement for the standard ip2long( ) function
//

function iptolong( $ip )
{
	$parts = explode(".", $ip);

	return $parts[0] > 127 ? ((ip2long($ip) & 0x7FFFFFFF) + 0x80000000) : ip2long($ip);
}

//
//  <integer> ipcmp( <string> $a, <string> $b )
//
//  Like strcmp(), but for IP addresses
//

function ipcmp( $a, $b )
{
	return iptolong($a) - iptolong($b);
}

?>