How to get dyndns via php

Use gethostbyname , it will return the IP ( IPv4) corresponding to the address, eg:

<?php
$ip = gethostbyname('meu_host_foo_bar.dyndns.org');

echo $ip;

An important detail is that if gethostbyname fails to get the ip address it will return the host itself which may confuse, so you can check it like this:

<?php
$hostname = 'meu_host_foo_bar.dyndns.org';
$ip = gethostbyname($hostname);

if ($ip === $hostname) {
    echo 'Falha ao obter o IP de: ', $hostname;
} else {
    echo 'IP:', $ip;
}

Note that you can try using gethostbynamel that will return a list in an array corresponding to the last hostname:

<?php
$hostname = 'meu_host_foo_bar.dyndns.org';
$ips = gethostbynamel($hostname);

if (!$hosts) {
    echo 'Falha ao obter o IP de: ', $hostname;
} else {
    print_r($hosts);
}

It will return something like:

Array
(
    [0] => 192.0.34.166
)

That is, depending on the service you can return more than one, then you can check what you need. Failure to do so will return false .