I saved my deviceID in the local storage of the browser with javascript:
<button onclick="store()" type="submit">Zoeken</button>
<script type="text/javascript">
//Store deviceID in local storage on button click
function store(){
var inputDeviceID= document.getElementById("deviceID");
localStorage.setItem("deviceID", inputDeviceID.value);
}
</script>
Now I want to look with php if any data is stored into the local storage and if there is data stored when opening the page go to that URL path, ../sigfoxapp/?deviceID=1B2E4F
$FOLDER = '../sigfoxdata/';
$dir = scandir($FOLDER);
$file = $_GET['deviceID'].'.json' ?: 'DEMO.json';
$fileUrl = $FOLDER.$file;