IP range

[thoand]

How can I check if my IP is in a range.
I have searched for the topic without success

eg.
if my ip is 193.214.1.123

And I want to check if I am in this range

193.214.1.0 - 193.214.1.255

any ideas,

regards Thomas

[swr]

The way to do it is to convert the IP address into a form where you can do comparisons on it.

The obvious way to do it would be to convert it to a 32-bit int, but ints in PHP are signed, so that won't work right. We can convert it to a string though, and do string comparisons...

function normalize_ip($ip) {
    list($a, $b, $c, $d) = explode('.', $ip);
    return sprintf('%03d%03d%03d%03d', $a, $b, $c, $d);
}

$ip = normalize_ip('193.214.1.123');
$start = normalize_ip('193.214.1.0');
$end = normalize_ip('193.214.1.255');

if ($ip >= $start && $ip <= $end) {
    echo "IP is valid.";
}
else {
    echo "IP is not in the allowed range.";
}
                                                                                

The normalize_ip function just takes the IP address, turns each octet into a three-digit number, and joins them into a 12-digit number. It's really a string but string comparisons are easy in PHP. DO NOT attempt to do math on that string, as it will cause it to turn into an int and it'll overflow (as a number it is too big for PHP to easily handle).

[drknow]

how do you get the ip address in the first place???

[swr]

$_SERVER['REMOTE_ADDR']

Take a look at the output of phpinfo() and you'll see a bunch of other variables too.

[AstroTeg]

Check out [man]ip2long[/man]. They include some work around the long integer issues with (s)printf() and "%u" (which ends up converting the long integer into a string). The beauty with this function is you can do bit masking with it. Which means you could mask IP subnets and do it from a SQL statement (assuming you store the long integer value in a database).

We implemented something like this to limit access to a subnet of an internal company to their intranet server (although it was done with MS SQL & ASP/JScript).