@wilirius I did some test on the url that was provided width this script :
<?php
$json = file_get_contents("http://connect.advancedcustomfields.com/index.php?a=get-info&p=pro");
$json = json_decode($json);
var_dump($json);
On localhost that works perfectly, I get a NULL with my host (OVH). I just wrote them and wait for their response.