Span kind is sending the "key" and not the "value".

[niborb]

Span.php

   /**
     * @inheritdoc
     */
    public function setTags(array $tags)
    {
        foreach ($tags as $key => $value) {
            if ($key === Tags\SPAN_KIND) {
                $this->span->setKind($key);
            } else {
                $this->span->tag($key, $value);
            }
        }
    }

When sending "SERVER" as kind. This results in the following request to zipkin.

{
  "id": "135c06ebadb41afd",
  "name": null,
  "traceId": "4025e5b35764428e",
  "parentId": "2cfb99b737a023d2",
  "timestamp": 1516363039462689,
  "duration": 8438045,
  "debug": false,
  "localEndpoint": {
    "serviceName": "*****",
    "ipv4": "127.0.0.1",
    "port": 80
  },
  "kind": "span.kind"
}

I think setKind should be passed the $value instead of $key

[jcchavezs]

Hi @niborb! Thanks again for the heads-up. There is a PR to solve this #7. Feel free to open PRs if you want to contribute.