Highchart not showing from JSON data - php

Question

I'm trying to display a line chart with json data, but with there, $_GET from the json I have the chart doesn't appear, here's my code :
$(function () {
var chart;
$(document).ready(function() {
$.getJSON("master/proyek/s-curve.php", function(json) {
chart = new Highcharts.Chart({
chart: {
renderTo: 'scurve',
type: 'line'
},
credits: {
enabled: false
},
title: {
text: 'S-Curve Balai'
},
subtitle: {
text: ''
},
xAxis: {
categories: ['M1', 'M2', 'M3', 'M4']
},
yAxis: {
title: {
text: ''
},
plotLines: [{
value: 1,
width: 1,
color: '#808080'
}]
},
tooltip: {
formatter: function() {
return '<b>'+ this.series.name +'</b><br/>'+
this.x +': '+ this.y;
}
},
legend: {
layout: 'horizontal',
},
plotOptions: {
line: {
dataLabels: {
enabled: true,
distance: 100,
}
}
},
series: json,
});
});
});
});
and this my s-curve.php :
<?php
header("Content-type: application/json");
require_once "config/database.php";
$db = new database();
$mysqli = $db->connect();
$balai = mysqli_real_escape_string($mysqli, $_GET['balai']);
if ($balai == 'bl-1') {
$sql = "SELECT plan, actual FROM scurve1 ORDER BY id ASC";
} else if ($balai == 'bl-2') {
$sql = "SELECT plan, actual FROM scurve2 ORDER BY id ASC";
} else if ($balai == 'bl-3') {
$sql = "SELECT plan, actual FROM scurve3 ORDER BY id ASC";
}
$hasil = array();
$hasil['name'] = 'Plan';
$result = $mysqli->query($sql);
while ($data = $result->fetch_assoc()) {
$hasil['data'][] = $data['plan'];
}
$hasil1 = array();
$hasil1['name'] = 'Actual';
$result = $mysqli->query($sql);
while ($data = $result->fetch_assoc()) {
$hasil1['data'][] = $data['actual'];
}
$nilai = array();
array_push($nilai, $hasil);
array_push($nilai, $hasil1);
print json_encode($nilai, JSON_NUMERIC_CHECK);
$mysqli->close();
display my json from localhost/master/proyek/s-curve.php?balai=bl-1 :
Display Json Data
from my case above, can someone tell what error I can fix to be able to display the chart.