lib/Attachment.php
protected function determineFileType($path)
    {
        if (!function_exists('finfo_open')) {
            // File info functions not available
            return;
        }

        // Determine file type
        $finfo = finfo_open(\FILEINFO_MIME_TYPE);
        $type = finfo_file($finfo, $path);

        finfo_close($finfo);

        if ($type === false) {
            // Could not determine file type
            return;
        }

        return $type;
    }
protected function determineFileType($path)
    {
        if (!function_exists('finfo_open')) {
            // File info functions not available
            return;
        }

        // Determine file type
        $finfo = finfo_open(\FILEINFO_MIME_TYPE);
        $type = finfo_file($finfo, $path);

        finfo_close($finfo);

        if ($type === false) {
            // Could not determine file type
            return;
        }

        return $type;
    }
@param string $path

@throws \RuntimeException

@return string