IIRC, i've helped you over PM a long time ago to fetch the data from the NLG-BTC api's of bleutrade.com, bittrex.com and litebit.eu. I've searched my PM archive, and here's the code:
<?php
$url = 'https://www.litebit.eu/requests/jsonp.php?call=nlg';
$response = file_get_contents($url);
$obj = json_decode($response, true);
echo 'sell : '. $obj['sell'] . '<br>';
?>
<?php
$url = 'https://bleutrade.com/api/v2/public/getticker?market=NLG_BTC';
$response = file_get_contents($url);
$obj = json_decode($response, true);
echo 'ask : '. $obj['result'][0]['Ask'] . '<br>';
?>
<?php
$url = 'https://bittrex.com/api/v1.1/public/getmarketsummary?market=btc-nlg';
$response = file_get_contents($url);
$obj = json_decode($response, true);
echo 'Bid : '. $obj['result'][0]['Bid'] . '<br>';
?>
You'll need to save this data (or any other data you can fetch from an api) in your database instead of showing it on your screen, and use one of the open source tools to make a graph...
