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Re: [PHP] Cause of undefined offset notice




Most probably an IP-address with only 2 dots.
$ php -r 'list($a, $b, $c, $d) = explode(".", "127.0.0");'
PHP Notice:  Undefined offset: 3 in Command line code on line 1

Martijn van Duren

On 11/17/17 21:42, Jennifer wrote:
> Hello,
> 
> 	I have a script that compares a visitors IP address against a file of known bad addresses but I'm getting this notice:
> 
> Notice: Undefined offset: 3 (line 26 below)
> 
> 	Can anyone see what I've done wrong?  Perhaps this sub was not written correctly to begin with?
> 
> Thank you,
> Jenni
> 
> -----------------------------------------------------------
> 
> function validate_ip($ip_array, $cm) {
> 	$msg = '';
> 	if (isset($cm['bad_ip_message'])) {
> 		$msg = $cm['bad_ip_message'];
> 	}
> 	if (@strpos( $cm['remote_ip'], ':' ) !== false) { return false; }  // Skip IPv6 addresses (?).
> 
> 	if (!is_array($ip_array)) { return false; }
> 	foreach ($ip_array as $banned_ip) {
> 		$banned_ip = trim($banned_ip);
> 		if ($banned_ip[0] === '#' || $banned_ip === '') { continue; }  // Skip comments and blank lines.
> 		
> 		if ( @strpos( $banned_ip, '/' ) === false ) {
> 			if (ip2long($banned_ip) === ip2long($cm['remote_ip'])) {
> 				ban_message($msg);
> 			}
> 			if (substr($banned_ip, -1) == '0') {
> 				$banned_ip .= '/24';  // Create a CIDR if IP ends in '0'.
> 			} 
> 		} 
> 		if ( @strpos( $banned_ip, '/' ) !== false ) {
> 			// Get the base and the bits from the CIDR.
> 			list($base, $bits) = explode('/', $banned_ip);
> 
> 			// Now split it up into it's classes.
> 			list($a, $b, $c, $d) = explode('.', $base);  // Notice: Undefined offset: 3
> 
> 			// Now do some bit shifting/switching to convert to ints.
> 			$i    = ($a << 24) + ($b << 16) + ($c << 8) + $d;
> 			$mask = $bits == 0 ? 0: (~0 << (32 - $bits));
> 
> 			// Here's our lowest int.
> 			$low = $i & $mask;
> 
> 			// Here's our highest int.
> 			$high = $i | (~$mask & 0xFFFFFFFF);
> 
> 			// Now split up the IP we're checking against into classes.
> 			list($a, $b, $c, $d) = explode('.', $cm['remote_ip']);
> 
> 			// Now convert the IP we're checking against to an int.
> 			$check = ($a << 24) + ($b << 16) + ($c << 8) + $d;
> 
> 			// If the IP is within the range, including highest/lowest values,
> 			// then it's within the CIDR range.
> 			if ($check >= $low && $check <= $high) {
> 				ban_message($msg);
> 			}
> 		}
> 	}
> 	return;
> }
> 

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