You would have to keep a counter on your side to record the number of queries youve made.  We do enforce a 5000 queries per 24 hour period, starting from the first query.  When you hit the magic 5k, youll get a 503 header and a page this xml response

<response success="false">
      <error>rate limit exceeded</error>
</response>

What I would do

Change
$urlchecker = file_get_contents($url);
to
$urlchecker = @file_get_contents($url);

It does fail from time to time.  For your debugging, what does

var_dump($result);var_dump($urlchecker);

show after each remote file pull?

You might also consider caching your results as each query will generate another query.  The logic is easy

You can download my vb mod vbstopforumspam from www.fizzleblood.net/vbStopForumSpam_v0.61.zip

Its not the most ideal caching as it has a broken logic to it.  If you make the primary key unique and sort by date desc limit 1, then you get the most recent result.  Ive fixed it in v0.62 but havent tested it properly.

I do this *a lot* for debugging my code

    $urlchecker = file_get_contents($url);
    $var_dump($urlchecker);exit;

and

    $result = curl_exec($curl);
    var_dump($result);exit;

Thanks very helpful,
I will try and get a dev over at punbb to give it the look over
to incorporate the caching...
I'll also point to that good mod you've made...

Im not familiar with the internals of phpbb but I hope

$query = array(
'INSERT'   => 'ip, bot_visit, lastseen, frequency',
'INTO'     => 'stopforumspam',
  'VALUES'   => '\''.$ip.'\', NOW(), \''.$xml["response"]

handles duplicate primary key inserts/updates

Force of habit in my typing The new site, to upgrade this one, has fluxbb 1.4 as its forum now.  Ill add this mod to the new version of the downloads page as I want to have this site running asap, just need to find the time where four projects arent pulling on each limb at the same time.