JacobBennett\Http2ServerPush\Middleware\AddHttp2ServerPush::buildLinkHeaderString PHP Метод

    private function buildLinkHeaderString($url)
    {
        $linkTypeMap = ['.CSS' => 'style', '.JS' => 'script', '.BMP' => 'image', '.GIF' => 'image', '.JPG' => 'image', '.JPEG' => 'image', '.PNG' => 'image', '.TIFF' => 'image'];
        $type = collect($linkTypeMap)->first(function ($extension) use($url) {
            return str_contains(strtoupper($url), $extension);
        });
        return is_null($type) ? null : "<{$url}>; rel=preload; as={$type}";
    }