public function depth(string $symbol, int $limit = 100)
    {
        if (is_int($limit) === false) {
            $limit = 100;
        }

        if (isset($symbol) === false || is_string($symbol) === false) {
            // WPCS: XSS OK.
            echo "asset: expected bool false, " . gettype($symbol) . " given" . PHP_EOL;
        }
        $json = $this->httpRequest("v1/depth", "GET", [
            "symbol" => $symbol,
            "limit" => $limit,
        ]);
        if (isset($this->info[$symbol]) === false) {
            $this->info[$symbol] = [];
        }
        $this->info[$symbol]['firstUpdate'] = $json['lastUpdateId'];
        return $this->depthData($symbol, $json);
    }