PHP + MySQL - Display empty entries in a Google bar chart - php

Question

I'm trying to implement an import/export per month graph for my website using Google Charts API with a MySQL database. Everything is ok, but I'm looking for a way to show in my chart also the months without imports or exports. Could someone please help me? Here is a screenshot of my graph, as you can see some months missing
<div id="columnchart_material" style="width: 800px; height: 500px;"></div>
<script type="text/javascript">
google.charts.load('current', {'packages':['bar']});
google.charts.setOnLoadCallback(drawChart);
function drawChart() {
var dati = google.visualization.arrayToDataTable([
['Month', 'Imports', 'Exports'],
<?php
$q = "SELECT month(date) AS month, SUM(imports) AS imports, SUM(exports) AS exports FROM table WHERE year(date)=2020 GROUP BY month(date)";
$res_q=mysqli_query($db,$q);
//fetch data
while ($row = mysqli_fetch_array($res_q)) {
$entry = "['".$row{'month'}."',".$row{'imports'}.",".$row{'exports'}."],";
echo $entry;
}
?>
]);
var options = {
chart: {
title: 'Imports and Exports',
subtitle: 'Bar chart',
}
};
var chart = new google.charts.Bar(document.getElementById('columnchart_material'));
chart.draw(dati, google.charts.Bar.convertOptions(options));
}

Answer 1

Consider the following:
<?php
$array = array(1,2,3,5,7,11);
for($i=1;$i<=12;$i++){
if(in_array($i,$array)){echo $i.' yes<br>';} else {echo $i.' no<br>';}
}
?>

Answer 2

You can use an additional array that holds your data and that contains all the months:
<?php
// prepare array with default 'empty' data
$entries = []
for ($m = 1; $m <= 12; $m++) {
$entries[$m] = '[]';
}
And then add the existing data to this array by overwriting the default values:
// fetch data
while ($row = mysqli_fetch_array($res_q)) {
$entries[$row['month']] = "['".$row{'month'}."',".$row{'imports'}.",".$row{'exports'}."]";
}
// output
echo implode(',', $entries);