code: protected function parseMetadataHeaders($headers = array())
      {
          // Validate
          if (!is_array($headers)) {
              return array();
          }
  
          // Return metadata
          $metadata = array();
          foreach ($headers as $key => $value) {
              if (substr(strtolower($key), 0, 10) == "x-ms-meta-") {
                  $metadata[str_replace("x-ms-meta-", '', strtolower($key))] = $value;
              }
          }
          return $metadata;
      }
docs: Parse metadata headers
  
  @param array $headers HTTP headers containing metadata
  @return array