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strata_ranger at hotmail dot com ¶
15 years ago
If the input string is not a readable IP address, inet_pton() generates an E_WARNING and returns FALSE.  The same is true for inet_ntop().

Also, inet_pton() does not recognize netmask notation (e.g: "1.2.3.4/24" or "1:2::3:4/64") in the input string.  This differs from how some database systems (like postgreSQL) support IP address types, so if you need that sort of functionality when processing IP addresses in PHP you'll have to write it in yourself.

A rough example:

<?php

// Sample IP addresses
$ipaddr = '1.2.3.4/24'; // IPv4 with /24 netmask
$ipaddr = '1:2::3:4/64'; // IPv6 with /64 netmask

// Strip out the netmask, if there is one.
$cx = strpos($ipaddr, '/');
if ($cx)
{
  $subnet = (int)(substr($ipaddr, $cx+1));
  $ipaddr = substr($ipaddr, 0, $cx);
}
else $subnet = null; // No netmask present

// Convert address to packed format
$addr = inet_pton($ipaddr);

// Let's display it as hexadecimal format
foreach(str_split($addr) as $char) echo str_pad(dechex(ord($char)), 2, '0', STR_PAD_LEFT);
echo "<br />\n";

// Convert the netmask
if (is_integer($subnet))
{
  // Maximum netmask length = same as packed address
  $len = 8*strlen($addr);
  if ($subnet > $len) $subnet = $len;
  
  // Create a hex expression of the subnet mask
  $mask  = str_repeat('f', $subnet>>2);
  switch($subnet & 3)
  {
  case 3: $mask .= 'e'; break;
  case 2: $mask .= 'c'; break;
  case 1: $mask .= '8'; break;
  }
  $mask = str_pad($mask, $len>>2, '0');

  // Packed representation of netmask
  $mask = pack('H*', $mask);
}

// Display the netmask as hexadecimal
foreach(str_split($mask) as $char) echo str_pad(dechex(ord($char)), 2, '0', STR_PAD_LEFT);

?>
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