I tried Googling charts.js to have a look at their API documentation. What I found was nothing like the formats that you appear to be using.
I did manage to get a chart produced using google.visualization api (if that helps)
<?php
$getdata = '
{
"result": [
{
"ID": 1,
"Users": [
{
"UserObject": {
"UserName": "User1",
"-": {
"ID": 1
},
"0": "0"
},
"User": "User1",
"Amount": 10
},
{
"UserObject": {
"UserName": "User2",
"-": {
"ID": 1
},
"0": "0"
},
"User": "User2",
"Amount": 20
},
{
"UserObject": {
"UserName": "User3",
"-": {
"ID": 1
},
"0": "0"
},
"User": "User3",
"Amount": 15
}
],
"Reached": false,
"IsActive": true
}
],
"error": false,
"version": 1
}
';
$data = json_decode($getdata);
$users = $data->result[0]->Users;
$dataPoints = array( ['User', 'Amount'] );
foreach($users as $user):
$dataPoints[] = array( $user->User, $user->Amount );
endforeach;
$jdata = json_encode($dataPoints);
?>
<!DOCTYPE HTML>
<html>
<head>
<title>Test</title>
<meta http-equiv="content-language" content="en">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<script type="text/javascript" src="https://www.gstatic.com/charts/loader.js"></script>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.5.0/jquery.min.js"></script>
<script type='text/javascript'>
$().ready(function() {
google.charts.load('current', {'packages':['corechart']});
google.charts.setOnLoadCallback(drawChart);
// Draw the chart and set the chart values
function drawChart() {
var dataArray = JSON.parse($("#chart-values").val())
var data = google.visualization.arrayToDataTable(dataArray);
// Optional; add a title and set the width and height of the chart
var options = {
'title':'User Amounts',
'width':550,
'height':400,
'slices': {
0: {'color':'#2ecc71' },
1: {'color':'#3498db' },
2: {'color':'#95a5a6' },
3: {'color':'#9b59b6' },
4: {'color':'#f1c40f' },
5: {'color':'#e74c3c' },
6: {'color':'#34495e' }
}
};
// Display the chart inside the <div> element with id="piechart"
var chart = new google.visualization.PieChart(document.getElementById('myChart'));
chart.draw(data, options);
}
})
</script>
<style>
.container {
width: 80%;
margin: 15px auto;
}
</style>
</head>
<body>
<input type='hidden' id='chart-values' value='<?=$jdata?>'>
<div class="container">
<h2>Pie Chart Demo</h2>
<div id="myChart"></div>
</div>
</body>
</html>