long2ip()

(PHP 4, PHP 5, PHP 7)

将长整型转化为字符串形式带点的互联网标准格式地址（IPV4）

说明

long2ip(int $proper_address): string

long2ip()函数通过长整型的表达形式转化生成带点格式的互联网地址（例如：aaa.bbb.ccc.ddd ）。

参数

$proper_address

合格的地址，长整型的表达形式。

返回值

返回字符串的互联网 IP 地址。

更新日志

注释

Note:

在 32 位架构中，从string转换integer整型形式的 ip 地址将有可能导致错误的结果，因为结果数字超出了PHP_INT_MAX限制。

参见

• ip2long() 将 IPV4 的字符串互联网协议转换成长整型数字

If the function doesn't exist:
<?
  if (!function_exists("long2ip")) {
    function long2ip($long) {
      // Valid range: 0.0.0.0 -> 255.255.255.255
      if ($long < 0 || $long > 4294967295) return false;
      $ip = "";
      for ($i=3;$i>=0;$i--) {
        $ip .= (int)($long / pow(256,$i));
        $long -= (int)($long / pow(256,$i))*pow(256,$i);
        if ($i>0) $ip .= ".";
      }
      return $ip;
    }
  }
?>

Use these two functions to convert from and to numbers compatible to MySQLs INET_ATON and INET_NTOA
<?php
  function convertIpToString($ip)
  {
    $long = 4294967295 - ($ip - 1);
    return long2ip(-$long);
  }
  function convertIpToLong($ip)
  {
    return sprintf("%u", ip2long($ip));
  }
?>

I wanted to be able to pass an IP address in a URL always as an unsigned int. I then converted it back as shown below:
$ip_addr = "192.168.100.25"; // example IP address that converts to neg #
$s32int = ip2long($ip_addr);
$us32str = sprintf("%u",$s32int);        // convert to unsigned string
// display orig IP address, signed 32 bit version, unsigned 32 bit ver, 
// finally converted back to IP addr
printf("%s ,%d, %s, %s", $ip_addr, $s32int, $us32str, 
     long2ip(-(4294967296-$us32str)));
// tested on Linux/Apache PHP 4.1.2

If you're running a 32 bit machine you can get wrong IPs. To prevent from this just cast to float e.g. 
<?php
long2Ip32bit($ip){
  return long2ip((float)$ip);
}
?>

For a 32bit safe long2ip, which can accept string or signed integer input, try:
 function safelong2ip($long) {
  $binStr = sprintf("%032s", decbin((float)$long));
  if (strlen($binStr) != 32) {
   throw new Exception("Invalid IPv4 subnet!");
  }
  $ipArr = [];
  for ($i = 0; $i < 4; ++$i) {
   $ipArr[] = bindec(substr($binStr, $i*8, 8));
  }
  return implode('.', $ipArr);
 }

when importing ip-ranges to a mysql database using an INT(10) field - NOTE: that you will get problems when using intval() function!
copied from "cleong" : 02-Oct-2001 02:21
intval() handles overflow differently depending on the type of the argument.
<?php
// intval('10000000000') = 2147483647
// intval(1e10) = 1410065408
?>

Beware when processing values that are invalid, you may get values that are different based on the OS. For instance:
$ip = long2ip(pow(2,32)+1024);
On windows you get 255.255.255.255. On linux it's 0.0.4.0.
So it seems it would be important to make sure the long you're converting is in the correct range.