javascript - Highcharts with ajax / json -

this isn't problem highcharts rather more javascript function passes data. first off , java skills pretty basic .. , pretty damn bad honest. laughing @ code equivalent of laughing @ handy capped people :)

anyway, idea pretty simple , i'm feeding highcharts graphs network traffic gathered php script via snnp call.

the data encoded json_encode , output looks this: [1464786728000,13850896] first value current time , second value traffic measured in octets. i've included php script below.

now of works pretty , data gets collected , graphs plots in real time no issues. problem comes in have pass current value javascript function can deduct previous value current value i'm left difference between intervals. need multiply value 8 ... since i'm converting octets bits , divide poll interval. should rather simple reason i'm unable read previous variable when pass it.

i hope i'm making sense here ;)

function requestdata(previous) { var poll     = 1000;  $.ajax({    url: 'grabethertraffic.php?canopyip=<? echo $canopyip; ?>',    success: function(point) {       var series = chart.series[0] ;       shift = series.data.length > 20; // shift if series         // little formula figure out current thoughput on interface is.         // need deduct previous data current data when       // timeout expires , function fires again.    var bps = (series - previous) * 8 / poll;        // plot bps..     bps.addpoint(point, true, shift);                    // here's attempt pass current data function when fires again.     settimeout(function () { requestdata(series); }, poll);          },         cache: false     }); } 

php script...

<?php  // set json header include 'snmpiods.php'; $canopyip = $_request['canopyip']; $x = time() * 1000;  $gatherrx = getsnmpdata("$canopyip","1.3.6.1.2.1.2.2.1.10"); list($null, $gatherrx) = split(" ", $gatherrx, 2); settype($gatherrx, "integer");   header("content-type: text/json"); $ret = array($x, $gatherrx); echo json_encode($ret);  ?>