Using the Eve Central API with PHP - Fuzzwork Enterprises

We’re going back to basics here. One thing that many sites, which are using the SDE from Eve, want to do, is access price data from EVE Central api. I don’t do this myself, having a EMDR relay, and consumer to provide my market data, but back when I was starting out, I did this. It’s a pretty simple thing to do, the only pain in the neck being the data structures that PHP wants to use, when you’re using XML. It likes throwing in arrays where you don’t think it should, which can be a bit of a pain. If you ever need to debug this, var_dump() will be your friend, showing you exactly how the data has been structured.

So, here’s a fairly basic bit of code. It asks eve central for the information for Tritanium, then prints out the so called ‘Percentile’ price. This is the price if someone was to buy 5% of the market, then average the cost out. It’s handy for ignoring the outliers, if not entirely accurate. The code is more complicated than it needs to be, but we’ll get to why in the second example.

$typeid=34;
$url="http://api.eve-central.com/api/marketstat?regionlimit=10000002&typeid=".$typeid;
$pricexml=file_get_contents($url);
$xml=new SimpleXMLElement($pricexml);
$item=$xml->xpath('/evec_api/marketstat/type[@id='.$typeid.']');
$price= (float) $item[0]->sell->percentile;
$price=round($price,2);
echo $price;

Fairly simple, really. You get the type id for Tritanium, the url that will pull back the data from the forge, mash them together, then use file_get_contents to retrieve them. Please not, some PHP installs will stop this from working. There’s a more complicated version at the bottom which may get you round this; functionally identical but using curl instead of file_get_contents.
Once you have the output from EVE Central, you push it into the SimpleXML parser, grab the bit that’s just about tritanium (the XPath bit does this. This is the over complicated bit), then pull just the sell percentile out of it. The reason for the [0] is because the Xpath bit could have returned more than one entry. In this case it can’t, but the parser is taking the safe option and giving you an array. The (float) is there as without it, you’re dealing with a SimpleXML data type, which is a pain to do math with. (float) just converts it into a regular number.

Now for the more complicated version. Eve central allows for multiple items to be queried at the same time. This is why I put the xpath in there. It allows us to target a specific type being returned, rather than having to go through each in turn to see if it’s the one we want, before continuing.

    $typeids=array(34,35);
    $url="http://api.eve-central.com/api/marketstat?regionlimit=10000002&typeid=".join('&typeid=',$typeids);
    $pricexml=file_get_contents($url);
    $xml=new SimpleXMLElement($pricexml);
    foreach($typeids as $typeid)
    {
        $item=$xml->xpath('/evec_api/marketstat/type[@id='.$typeid.']');
        $price= (float) $item[0]->sell->percentile;
        $price=round($price,2);
        echo $typeid." ".$price."\n";
    }

This time, instead of a single type id, we’re asking for multiple. We store them in an array, then mash that array into the url, with a join (or implode) which adds the right number of &typeid= to it. Then it goes on as before until just after the xml is parsed, where it goes and grabs each individual element out in turn, iterating through the array.

If you wanted to pull the minimum buy price, you’d replace the $price= (float) $item[0]->sell->percentile; with $price= (float) $item[0]->buy->min; and so on. It’s fairly simple.

Now, the curl version, of the first bit of code:

$typeid=34;
$url="http://api.eve-central.com/api/marketstat?regionlimit=10000002&typeid=".$typeid;
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
$response = curl_exec($ch);
if($response === false)
{
    echo 'Curl error: ' . curl_error($ch);
}
else
{
    $xml=new SimpleXMLElement($response);
    $item=$xml->xpath('/evec_api/marketstat/type[@id='.$typeid.']');
    $price= (float) $item[0]->sell->percentile;
    $price=round($price,2);
    echo $price;
}

It’s a bit more complicated, but it gives you a way of dealing with a remote site not responding. Perhaps looking at a different site for price data, for example.

Remember, the more calls you have on remote sites, the slower your pages will be to load. Consider caching the price data locally, perhaps in a database, or if you have access to it, memcache (My preference. but it’s uncommon)

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