How to display data from database to chart using chart.js and ajax?

I want to display data from a database in a chart.
I want to display the data with date type input.
Whichever date value I select, the data for that date should be displayed. Ajax function sends the selected date to statisztika_datum_lekerdez.php with parameter q.
I tried it out to see if it really returns the received date value data. Using this:

  print json_encode($kiadas_ertek_osszes);
  print json_encode($kiadas_nev_osszes);

I get this back: [[1000],[8000]][[“food”],[“sport”]]
So the result is good. The problem is that it doesn’t show up in the chart.
How can I make the queried data appear in the chart?

Here is my code:

<?php
session_start();
require_once('connection.php');
?>
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/boxicons@latest/css/boxicons.min.css">
    <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
    <link rel="stylesheet" href="../css/statisztika.css">
    <title>Statisztika</title>
</head>

<body>

    <main id="main">

        <div class="container">


            <div id="tartarom">

                <!--?=============== Dátum ===============-->
                <form action="statisztika_datum_lekerdez.php" method="POST" id="statisztika_datum_form">
                    <input type="date" name="datum_lekerdezes" onchange="showData(this.value)" class="datum" id="datum_lekerdezes" required>
                </form>

                <div id="diagram_helye"> </div>

            </div>

        </div>

    </main>


    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="import { Chart, LineController, LineElement, PointElement, LinearScale, Title } from `chart.js`"></script>
    <script>
        function showData(str) {
            var xmlhttp = new XMLHttpRequest();
            xmlhttp.onreadystatechange = function() {
                if (this.readyState == 4 && this.status == 200) {
                    document.getElementById("diagram_helye").innerHTML = this.responseText;
                }
            };
            xmlhttp.open("GET", "statisztika_datum_lekerdez.php?q=" + str, true);
            xmlhttp.send();
        }
    </script>


</body>

</html>

<?php
session_start();
require_once('connection.php');
?>
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/boxicons@latest/css/boxicons.min.css">
    <script src="https://cdn.jsdelivr.net/npm/chart.js"></script>
    <link rel="stylesheet" href="../css/statisztika.css">
    <title>Statisztika</title>
</head>

<body>




    <?php
    require_once('connection.php');
    $q = ($_GET['q']);
    $id = $_SESSION['id'];
    $sql = "SELECT kategoria_nev, ertek FROM kiadas_tipusok_naponta WHERE user_id = $id AND datum = '$q'";

    $result = mysqli_query($conn, $sql);
    if (mysqli_num_rows($result) > 0) {

        $kiadas_ertek_osszes = array();

        foreach ($result as $row) {
            $kiadas_ertek_osszes[] = [
                $row["ertek"] * (-1)

            ];
        }
        foreach ($result as $row) {
            $kiadas_nev_osszes[] = [
                $row["kategoria_nev"]
            ];
        }
    } else {
        $kiadas_ertek_osszes[] = 0;
        $kiadas_nev_osszes[] = 0;
    }

    print json_encode($kiadas_ertek_osszes);
    print json_encode($kiadas_nev_osszes);

    ?>

    <div class="diagram_div">
        <canvas id="myChart_kiadasok"></canvas>
    </div>

    <script>
        const ctx = document.getElementById('myChart_kiadasok');
        const myChart_kiadasok = new Chart(ctx, {
            type: 'doughnut',
            data: {
                labels: <?= json_encode($kiadas_nev_osszes) ?>,
                datasets: [{
                    label: 'Kiadások (Ft)',
                    data: <?= json_encode($kiadas_ertek_osszes) ?>,
                    backgroundColor: [
                        '#fea37f86',
                        '#fbc53193',
                        '#3171fb93',
                        '#ffa600b6',
                        '#5fa8d398',
                        '#50db268e',
                        '#eb4e4b94',
                        '#3fd5e698'
                    ],
                    hoverOffset: 6,
                    borderColor: [
                        'white'
                    ],
                    borderWidth: 0.8,
                    Fontsize: 30
                }]
            },
            options: {
                plugins: {
                    title: {
                        display: true,
                        text: 'Kiadások típusai'
                    },
                    legend: {
                        display: true,
                        position: 'bottom'
                    }
                },
                scales: {
                    y: {
                        beginAtZero: true
                    }
                }
            }
        });
    </script>

    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <script src="import { Chart, LineController, LineElement, PointElement, LinearScale, Title } from `chart.js`"></script>



</body>

</html>