Hi,
I asked some PHP Experts and they provide me with a solution.
You have to use this PHP Code:
<?php
// Reading data from sensor and show it
$json = json_decode(file_get_contents("https://iot.seeed.cc/v1/node/GroveMoistureA0/moisture?access_token=xxxxxxxxxxxxxxxxxxxxxxxxxxxxx"));
echo $json->moisture;
fclose($json);
?>
Thanks
Michael