SOS Alarm POST Method

Hi, im creating a web service to receive the unit id when the sos notification is activated sending it through a request post method to app ip address.
Looks like this:

<?php
$id = "00000000"; //<--POST VARIABLE EXAMPLE
?>
<script>
var info = wialon.core.Session.getInstance().getItem("<?php echo $id; ?>"); // get unit by id
</script>

however i dont know how can i receive the post variable through php (for example $id=$_POST['name'];)
does any know how the variable is named or how can i get the post data??
thanks