IP range check in PHP - This function checks if a given IP address is in a given IP range. It should be much more efficient than the ip2long / long2ip functions that come with PHP that can only be used for IPv4 and have polynomial costs

testIpRange.php

<?php
/*
	> CONTACT:
		Jan Hendriks
		http://www.gawe-design.de
		[email protected]
	> DESCRIPTION:
		The functions (you can also use them via php-include) checks if a given IP is in a given IP range
		These functions are much more efficient than the ip2long / long2ip functions from php that can only be used for IP v4 and have polynomial costs
		These functions are about O(number of positions), e.g. IP v.4: O(4); (I think)
		And without all these stupid comments it is really tiny!
	> EXAMPLE OF USE:
		You could use them for example as follows:
			// remove the $ip, $ipra, $ipre and echo lines on top of this file
			include("testip.php");		// In your script
			$ip="127.0.01";			// Define the IP to check
									// e.g. $ip = gethostbyname("www.dahoc.de.vu"); whereas 'gethostbyname' feature has to be enabled by server
			$ipra="127.0.0.0"			// Your IP range start, has to be "smaller" or equal than the IP range end
			$ipre='127.0.0.255';		// Your IP range end
			echo '<br/>IP is '.(isInIpRange($ip) ? '' : 'not ').'in the given range';	// The actual invocation of the check, taken from below
	> COPYRIGHT:
	 	no reproduction without my permission (please just ask me first)
	> Comments, corrections, requests, suggestions, bugfixes, complaints and questions are always welcome
*/
$ip='127.9.9.9.9.9';	// example IP to check
// IP-Range start and end
// IMPORTANT: start-IP has to be smaller or equal than end-IP!
// IMPORTANT AND OBVIOUS: IP range has to have the same length of the IP to check!
$ipra='127.0.0.1.5.2';	// example IP range start
$ipre='127.9.9.9.9.9';	// example IP range end
echo '<br/>IP ('.$ip .') is '.(isInIpRange($ip) ? '' : 'not ').'in the given range ('.$ipra.' - '.$ipre.')';	// Explicitly: if (isInIpRange($ip)) { /* IP is in range */ } else { /* IP is out of range */ }
// boolean function checks if given IP address matches IP Range
/** @return true: IP address is in IP range
@return false: IP address is out of IP range **/
function isInIpRange($theip) {
	global $ipra;
	global $ipre;
	// Split those numbers up, no matter if this is IP v4, IP v6, ...
	$aip=(array)explode('.',$theip);
	// IP is 'not in Range' easier to check than 'IP is in range':
	// That's because if the first if (testip()...) fails, the second is needless, so that we thus save some cost
	// Check if IP is not smaller than starting IP and is not bigger than ending IP = IP is in range
	return (bool)( (testIp($aip,(array)explode('.',$ipra)) != -1) && (testIp($aip,(array)explode('.',$ipre)) != 1) );
}
// recursive function compares 2 (IP) numbers
/** @return -1: First number smaller than second
@return 1: First number bigger than second
@return 0: First and second number equal **/
// $i specifies the position of the check, initialized with 0 (top position of IP-Tuple)
function testIp($theip,$theipr,$i=0) {
	switch (TRUE) {
		case ($theip[$i] < $theipr[$i]): return (int)-1;
		case ($theip[$i] > $theipr[$i]): return (int)1;
		case (count($theip) == ($i+1)): return (int)0;			// Last position of the IP-tuple reached and additional all numbers up to this place are equal => Return equal: 0
		default: return (int)testIp($theip,$theipr,++$i);	// If equal at current position, check next position (recursive)  e.g. 127.x.y.z == 127.k.l.m (next would be to test position x against k, y against l, etc.)
	}
}
?>