public static function getIconByExtension($extension)
    {
        if ('pdf' === $extension) {
            return 'file-pdf-o';
        }

        if (true === in_array($extension, self::extensionsArchive())) {
            return 'file-archive-o';
        }

        if (true === in_array($extension, self::extensionsImage())) {
            return 'file-image-o';
        }

        if (true === in_array($extension, self::extensionsCode())) {
            return 'file-code-o';
        }

        if (true === in_array($extension, self::extensionsVideo())) {
            return 'file-video-o';
        }

        if (true === in_array($extension, self::extensionsAudio())) {
            return 'file-audio-o';
        }

        if (true === in_array($extension, self::extensionsExcel())) {
            return 'file-excel-o';
        }

        if (true === in_array($extension, self::extensionsPowerPoint())) {
            return 'file-powerpoint-o';
        }

        if (true === in_array($extension, self::extensionsWord())) {
            return 'file-word-o';
        }

        return null;
    }