Compute signature of a http from Hoiio. This is used to authenticate the notification from Hoiio. Match this computed signature with the HTTP header "X-Hoiio-Signature".

hoiio_signature.php

<?php

function computeHoiioSignature($payload, $accessToken) {
  // hash_hmac will return a hex of the digest
	$signature =hash_hmac('sha256', $payload, $accessToken);
	return $signature;
}

?>