PHP inet_ntop() is acting differently on real VPS - php

Question

I deployed my application on a VPS and It works fine expect the inet_ntop() function. On my local web server it's working fine with no error message.
I store the IP addresses in a binary(16) column. Before I would store them into the database I convert them. My last login IP is: 4e43b7, in binary numbers: 00110100 01100101 00110100 00110011 01100010 00110111 and the readable format: 78.92.67.183. So it run with a warning message on the VPS: Warning: inet_ntop(): Invalid in_addr value in home/...
What's wrong? According to the PHP doc the function works on PHP 5.1 or higher and a VPS has 5.5, but I am using 5.6. Can version differences cause problem? This line causes the warning:
$ip = inet_ntop($datas['ip_address'];

Answer 1

As per the manual:
When BINARY values are stored, they are right-padded with the pad value to the specified length. The pad value is 0x00 (the zero byte).
so you're not pulling out a 32bit IPv4 address. You're pulling out an 16x8bit = 128bit value, and feeding that to inet_ntop().

Answer 2

As Marc B noted, your BINARY column is being right-padded with zeroes which is then throwing off your decoding. There's not a super good way of handling this, particularly within just MySQL.
However, IPv6 has a built-in method of encapsulating IPv4 addresses, 6to4. Using this you can store v4 and v6 addresses side-by-side in a way that's maintainable and easy to deal with.
function fourToSix($addr) {
$haddr = str_pad(dechex(ip2long($addr)), 8, '0', STR_PAD_LEFT);
$v6 = sprintf('2002:%s::', implode(':', str_split($haddr, 2)));
return $v6;
}
function sixToFour($addr) {
return long2ip(hexdec(implode('', array_slice(explode(':', $addr), 1, 4))));
}
function isSixToFour($addr) {
return explode(':', $addr)[0] == '2002';
}
$v4 = '10.1.2.3';
$v6 = '2002:0a:01:02:03::';
var_dump(
fourToSix($v4),
isSixToFour($v6),
sixToFour($v6),
bin2hex(inet_pton($v6))
);
Output:
string(18) "2002:0a:01:02:03::"
bool(true)
string(8) "10.1.2.3"
string(32) "2002000a000100020003000000000000"
edit
Example store:
$stmt = $dbh->prepare('INSERT INTO table (id, addr) VALUES(?, ?);');
// convert IP if it is v4
if( ip2long($ip_addr) !== false ) {
$ip_addr = fourToSix($ip_addr);
}
$stmt->execute(1, inet_pton($ip_addr));
Example retrieve:
$addr_raw = $dbh->query('SELECT addr FROM table WHERE id=1')->fetch(PDO::FETCH_ASSOC)['addr'];
$addr_str = inet_ntop($addr_raw);
if( isSixToFour($addr_str) ) {
printf("IPv4 address is: %s\n", sixToFour($addr_str));
} else {
printf("IPv6 address is: %s\n", $addr_str);
}