Example PHP code for handling a webhook callback from Data Basin

databasin_webhook.php

<?php
$SECRET_KEY = "<secret key here>";

function base64url_encode($data) { 
  return rtrim(strtr(base64_encode($data), '+/', '-_'), '='); 
} 

function is_valid($secret, $value, $salt, $signature) {
    $verify = base64url_encode(hash_hmac("sha1", $value, sha1($salt . $secret, true), true));
    return $signature === $verify;
}

if (array_key_exists("HTTP_X_WEBHOOK_SIGNATURE", $_SERVER)) {
    $body = file_get_contents("php://input");
    $raw_signature = $_SERVER['HTTP_X_WEBHOOK_SIGNATURE'];
    list($salt, $signature) = explode(":", $raw_signature, 2);

    // Verify the request body against the signature/salt combination.
    if (!is_valid($SECRET_KEY, $body, $salt, $signature)) {
        die("Invalid signature!");
    }

    // We've confirmed that the request really is from Data Basin
    $payload = json_decode($body);
    echo($payload->event);
}
else {
    die("No signature!");
}
?>