Aerys\StandardResponse::push PHP Method

    public function push(string $url, array $headers = null) : Response
    {
        if ($this->state & self::STARTED) {
            throw new \LogicException("Cannot add push promise; output already started");
        }
        \assert((function ($headers) {
            foreach ($headers ?? [] as $name => $header) {
                if (\is_int($name)) {
                    if (count($header) != 2) {
                        return false;
                    }
                    list($name) = $header;
                }
                if ($name[0] == ":" || !strncasecmp("host", $name, 4)) {
                    return false;
                }
            }
            return true;
        })($headers), "Headers must not contain colon prefixed headers or a Host header. Use a full URL if necessary, the method is always GET.");
        $this->headers[":aerys-push"][$url] = $headers;
        return $this;
    }