How do I summarise CIDR addresses in PHP?

You'll need to use the binary operators in PHP (| & << >> etc).
Then you can use the convert-to-binary functions to convert between int and bin.

I assume you know how to calculate summaries with CIDR addressing.

// &	AND
// |	OR
// >>	right-bit-shift
// <<	left-bit-shift
// ^	XOR
$a = 8;
$b = 5;
$c = $a | $b;
echo $c .'<br>';// Prints 13
 
$a = 46;
$b = 248;
$c = $a & $b;
echo $c .'<br>';// Prints 40
 
$a = 10;
$b = 5;
$c = $a ^ $b;
echo $c .'<br>';// Prints 15
 
$a = 128;//10000000
$b = 1;
$c = $a >> $b;//0100000
echo $c .'<br>';// Prints 64
 
$a = 6;//110
$b = 2;
$c = $a << $b;//11000
echo $c .'<br>';// Prints 24

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Bitwise operators give me too much of a head ache, possibly the worst aspect of writing code. Otherwise, I could simply transcode the Perl/Ruby variants. I was hoping for a ready solution.

Sorry for that! I searched Google and it didn't come up with anything useful. I want to make a real code that works but this weekend I don't have the time. Maybe tonight when I come home. I'm a nightowl! One question though... are the IP-addresses you submitted already summarized? (I think they are) If so, can you please send some example IP-addresses that should be summarized.

For example: Any IPs that summarize into 58.84.240.0/20.

The example was not a good one... below is one that summarises better. If you do take the time to write one, make sure to leave a point of contact as I doubt some points here are enough reward :)

# Summarised (9 CIDR addresses)
58.147.128.0/19
117.55.192.0/20
121.100.48.0/21
125.213.192.0/19
202.56.176.0/20
202.86.16.0/20
203.215.32.0/20
210.80.0.0/19
210.80.32.0/19
 
# Unsummarised (72 CIDR addresses)
58.147.128.0/19
62.142.210.32/27
63.243.149.0/27
63.243.150.8/29
63.243.150.16/28
64.86.63.64/27
80.247.139.0/24
82.205.190.0/23
82.205.192.0/21
82.205.202.0/23
82.205.204.0/22
82.205.246.0/25
84.11.26.128/26
84.11.33.0/24
84.11.79.0/24
87.249.84.0/24
117.55.192.0/20
117.104.224.0/21
121.100.48.0/21
121.127.32.0/19
125.213.192.0/19
202.56.176.0/20
202.86.16.0/20
202.133.9.240/28
202.133.13.8/29
202.133.13.16/28
202.133.13.40/29
202.133.13.56/29
202.133.13.96/28
202.174.133.8/29
202.174.133.32/28
202.174.133.144/29
202.174.134.0/29
202.174.144.0/29
202.174.144.216/29
202.174.148.48/29
202.174.148.128/29
202.174.153.184/29
202.174.154.0/29
202.174.154.24/29
202.174.154.96/28
202.174.154.128/29
202.174.154.160/29
202.174.154.180/30
202.174.154.184/30
202.174.154.212/30
202.174.155.128/29
202.174.155.144/29
202.174.155.216/29
202.174.155.240/29
202.174.156.64/26
202.174.156.192/28
202.174.156.208/29
202.174.156.248/29
202.174.157.192/27
202.174.157.232/29
203.88.66.64/29
203.88.66.160/29
203.88.82.240/29
203.88.88.24/29
203.88.88.32/29
203.88.88.40/30
203.88.88.160/29
203.88.88.224/29
203.208.205.192/26
203.215.32.0/20
208.35.53.176/28
210.5.226.0/24
212.116.232.208/28
217.10.167.0/24
217.195.144.24/29
217.195.144.32/30

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BTW, this was data from 2 different sources covering Afghanistan's IP ranges (the country was only for example's sake). I think the unsummarised list is an older/newer list as there seems to be some ranges that are not represented in the summarised one.

Hmm, it was more difficult than I thought it should be. I'm too tired I have to much to do in school so I don't have the time. I have a problem with my code-logic, but I'm posting my code so far and some pseudo-code for you to try. I need to point out that I'm studying for the CCNA exam and so my CIDR knowledge is a bit bad, but I think I know how to calculate it (taking common bits and return network_address/bits). See pseudo for more details.

I am sorry for this but I hope you get a solution soon. You can e-mail me on waschman at gmail dot com when you find a solution. Good luck!

/**
 * Get single IP-address class
 *
 * @param string $ip
 */
function get_ip_class($ip)
{
	$class = false;
	$octet = explode('.', $ip);
	if ($octet[0] <= 126) $class = 'A';
	elseif ($octet[0] == 127) $class = 'Loopback';
	elseif ($octet[0] <= 191) $class = 'B';
	elseif ($octet[0] <= 223) $class = 'C';
	elseif ($octet[0] <= 239) $class = 'Multicast';
	else $class = 'Reserved';
	return $class;
}
 
 
/**
 * Enter description here...
 *
 * @param array $ip
 */
function summarize($ips)
{
	$count = count($ips);
	$octet_diff = 0;
	// Save all octets into an array
	for ($pos=0; $pos<4; $pos++) {
		for ($i=0; $i<$count; $i++) {
			$octets[$i] = explode('.', $ips[$i], 4);
			// Save first octet so we can check which octet differs from
			// the others. Crucial when we want to know where to begin checking
			// of binary digits.
			if ($i==0) $first = $octets[$i][$pos];
			// Find different octets
			if ($first != $octets[$i][$pos]) {
				$debug = $i .':'. $pos;//save which IP and octet
				$octet_diff = $pos;
				break;
			}
		}
	}
	
	echo 'Debug: Position of octet that differs is '. $debug .'<br>';
	
	// Logic problem here -- too tired and too much in to do in school instead
	
	// Some kind of main-loop.
	// Check the diffing octet in IP x and x+1.
	// Convert them both to binary (or leave as int).
	// Loop through binary positions, starting from the left.
	// Is ANDing y bit of octet in IP x y bit of octet in IP x+1 equal to 1?
	// If 1 goto next loop.
	// Now compare y bit of octet in IP x+1 and x+2.
	// Is ANDing equal to 1?
	// And so on...
	//
	// Loop through y bit of all IP:s passed to summarize().
	// If every ANDing did get 1 move on to y+1 bit.
	// And repeat above until you encounter an ANDing equal to 0.
	// If 0 then we have all the bits needed to summarize the IP-addresses.
	//   We only have to keep track of the number of bits tested from left
	//   to right to have the number of bits used for the subnetmask.
}
 
 
 
// Should summarize into 192.168.16.0/20
$ip[] = '192.168.1.0';
$ip[] = '192.168.2.0';
$ip[] = '192.168.3.0';
$ip[] = '192.168.4.0';
$ip[] = '192.168.5.0';
$ip[] = '192.168.6.0';
$ip[] = '192.168.7.0';
$ip[] = '192.168.8.0';
$ip[] = '192.168.9.0';
$ip[] = '192.168.10.0';
 
$cidr_ip = summarize($ip);
echo '<p>'. $cidr_ip .'</p>';

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