src/Message/Stream/AbstractStream.php
public function getMetadata($key = null)
    {
        if (null === $key) {
            return stream_get_meta_data($this->stream);
        }
        $metadata = stream_get_meta_data($this->stream);
        if (! array_key_exists($key, $metadata)) {
            return null;
        }
        return $metadata[$key];
    }
public function getMetadata($key = null)
    {
        if (null === $key) {
            return stream_get_meta_data($this->stream);
        }
        $metadata = stream_get_meta_data($this->stream);
        if (! array_key_exists($key, $metadata)) {
            return null;
        }
        return $metadata[$key];
    }
Get stream metadata as an associative array or retrieve a specific key.

The keys returned are identical to the keys returned from PHP's
stream_get_meta_data() function.

@link http://php.net/manual/en/function.stream-get-meta-data.php
@param string $key Specific metadata to retrieve.
@return array|mixed|null Returns an associative array if no key is
provided. Returns a specific key value if a key is provided and the
value is found, or null if the key is not found.