$target = new Target;
//update the Target URL if necessary with $target->setUrl($url)

$credential = new Credential;
$credential->setConsumerKey(123);
$credential->setConsumerSecret(456);

$client = new Mozilla\Marketplace\Client;
$client->setTarget($target);
$client->setCredential($credential);

// validate manifest
$response = $client->validateManifest('http://example.com/manifest.webapp');
echo "\n\nManifest id: ".$response['id'];
echo "\nManifest is ";
if ($response["valid"]) {
  echo "valid - creating webapp...";
  // create webapp
  $response = $client->createWebapp($response['id']);
  echo "\n\nWebapp id: ".$response['id'];
} else {
  echo "invalid";
}