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function validateIp($ip) {
/*
  Regex based on following list of bogons:
  0.0.0.0/8
  5.0.0.0/8
  10.0.0.0/8
  23.0.0.0/8
  36.0.0.0/8
  37.0.0.0/8
  39.0.0.0/8
  42.0.0.0/8
  49.0.0.0/8
  100.0.0.0/8
  101.0.0.0/8
  102.0.0.0/8
  103.0.0.0/8
  104.0.0.0/8
  105.0.0.0/8
  106.0.0.0/8
  127.0.0.0/8
  169.254.0.0/16
  172.16.0.0/12
  179.0.0.0/8
  185.0.0.0/8
  192.0.0.0/24
  192.0.2.0/24
  192.168.0.0/16
  198.18.0.0/15
  198.51.100.0/24
  203.0.113.0/24
  224.0.0.0/3
 */
$regex = '/^
  (?:
    0 |
    5\. |
    10\. |
    23\. |
    3[679]\. |
    42 |
    49 |
    10[0-6] |
    127 |
    179 |
    185 |
    22[4-5] |
    2(?:[34][0-9]|5[0-5]) |
    169\.254 |
    172\.(?:1[6-9]|[23][0-9])\. |
    192\.0\.[02]\. |
    192\.168\. |
    198\.(?:1[89]|51)\. |
    203\.0\.113
  )
/x';

return preg_match(
  '/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/', $ip) == 1 && 
  preg_match($regex, $ip) == 0;
}