php - 从 mysql 中检索数据并从 php 中输出 json

Question

我正在从 Arduino MCU 转储 json采用以下格式，

{"live" : [{"location" : "Outdoor" , "temperatureInC" : "33.90" , "temperatureInF" : "93.02" , "dewPoint_in_Fahr" : "21.18" , "dewPoint_in_Cel" : "-6.01" , "heat_index__in_Fahr" : "87.17" , "heat_index_in_Cel" : "30.65" , "humidity":"7.40" , "UVSig":"131.44"} , {"location" : "Drawing Room" , "temperatureInC" : "31.20" , "temperatureInF" : "88.16" , "dewPoint_in_Fahr" : "46.78" , "dewPoint_in_Cel" : "8.21" , "heat_index__in_Fahr" : "85.03" , "heat_index_in_Cel" : "29.46" , "humidity" : "24.00"}] , "pots" : [{"soilMoist" : "118", "avgSoilMoist" :"125" }]}

此数据是实时的，但我的 Arduino 也正在转储到 mysql 服务器。

我想使用 php 检索并在前端显示它

我对 php 知之甚少，写了下面的代码，成功地将数据从 mysql 服务器转储到浏览器中:

<?php
header('Content-type: application/json');

$servername = "localhost";
$username = "username";
$password = "secret";
$dbname = "arduinoData";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);
// Check connection
if ($conn->connect_error) {
     die("Connection failed: " . $conn->connect_error);
}

$sql = "SELECT  timeStamp, out_temperature, out_humidity FROM sensorLog ORDER BY timeStamp DESC LIMIT 1";
$result = $conn->query($sql);

if ($result->num_rows > 0) {
     // output data of each row
     while($row = $result->fetch_assoc()) {
         echo "<br>Time: ". $row["timeStamp"]. "<br>Temperature: ". $row["out_temperature"]. "<br>Humidity: " . $row["out_humidity"] . "<$
     }
} else {
     echo "0 results";
}

$conn->close();
?>

然而，这只会吐出两个 3 列的表，甚至没有正确的 json，我想使用 php 和转储 json 从 mysql 检索数据，格式与我从 arduino live 获得的格式相同，除了将按钮 live 替换为 database。

如果我想在客户端的前端页面上直播或从数据库中检索数据，这将很有用。任何帮助将不胜感激。我是 php 的新手。

Answer 1

要获取所有列，您需要选择 * 而不是查询中的 3 个特定列名。要获得有效的 JSON 对象，您只需使用 PHP json_encode 函数对结果进行编码，如下例所示:

$sql = "SELECT  * FROM sensorLog ORDER BY timeStamp DESC LIMIT 1";
$result  = $conn->query($sql);

$rows = $result->fetch_all(MYSQLI_ASSOC);
header('Content-Type: application/json');
echo json_encode($rows);

NOTE: You can always use json_decode to convert the JSON string back to the original results array.