Sensor Data To JSON

<?php
//robotzero.one

$sensorsData = '{';

$sensorsData .= '"peltier":';
$sensorsData .= '{"peltier_temp":';
$sensorsData .= $_GET['peltier_temp'];
$sensorsData .= ',"fan_speed":';
$sensorsData .= $_GET['fan_speed'];
$sensorsData .= '},';

$sensorsData .= '"sensor_temp":';
$sensorsData .= '{"air_temp":';
$sensorsData .= $_GET['air_temp'];
$sensorsData .= ',"processed_temp":';
$sensorsData .= $_GET['processed_temp'];
$sensorsData .= '},';

$sensorsData .= '"sensor_humidity":';
$sensorsData .= '{"air_humidity":';
$sensorsData .= $_GET['air_humidity'];
$sensorsData .= ',"processed_humidity":';
$sensorsData .= $_GET['processed_humidity'];
$sensorsData .= '}}';

file_put_contents('sensordata.txt', $sensorsData);
?>