Chart.js MySQL PHP时间刻度

Question

我想使用RPi，MySQLi，PHP和Chart.js绘制图形。我遵循了这个教程：

https://www.youtube.com/watch?v=2F5iTlPgaV8&t=138s

目前，我的图表是空的。 X轴是'未定义'，y轴的范围是错误的。 在我的情况下，x轴应显示时间格式值（HH：MM：SS）。有没有人知道如何从MySQL为Chart.js正确设置接收时间数据？

我也检查了这个解决方案，但它对我不起作用：

chart.js v2 - how to 'fill' the graph when using time scale

谢谢！

的index.php

<?php
$servername = "localhost";
$username = "airqualitysensor";
$password = "password";
$database = "temperatura";

$conn = new mysqli($servername, $username, $password, $database);

if ($conn->connect_error){
    die("Connection failed: ". $conn->connect_error);
    exit();
}

$sql = "SELECT * FROM temperaturaodczyt";
$result = $conn->query($sql);

$data = array();
foreach($result as $row){
    $data[] = $row;
    }
$result->close();
$conn->close();

print json_encode($data);
?>

app.js

$(document).ready(function(){
    $.ajax({
    url:"http://localhost/index.php",
    method: "GET",
    success: function(data) {
        console.log(data);

        var tczas = [];
        var temperatura = [];

        for (var i in data){

            tczas.push(data[i].tczas);
            temperatura.push(data[i].temperatura);

            }


        var chartdata = {
            labels: tczas,
            datasets : [
                {
                    label : "Zmierzona temperatura",
                    fill: false,
                    lineTension: 0.1,
                    backgroundColor: "rgb(200, 200, 200, 0.75)",
                    borderColor: "rgb(200, 200, 200, 0.75)",
                    hoverBackgroundColor: "rgb(200, 200, 200, 1)",
                    hoverBorderColor: "rgb(200, 200, 200, 0.75)",
                    data: temperatura
                }
                ]
            };

        var ctx = $("#mycanvas");

        var lineGraph = new Chart(ctx, {
            type: "line",
            data: chartdata
            });


        },
    error: function(data) {

        }
    });

});