HM\BackUpWordPress\Zip_File_Backup_Engine::backup PHP Method

    public function backup()
    {
        if (!$this->get_zip_executable_path()) {
            return false;
        }
        $command = array();
        // cd to the site root
        $command[] = 'cd ' . escapeshellarg(Path::get_root());
        // Run the zip command with the recursive and quiet flags
        $command[] = '&& ' . escapeshellcmd($this->get_zip_executable_path()) . ' -rq';
        // Save the zip file to the correct path
        $command[] = escapeshellarg($this->get_backup_filepath()) . ' ./';
        // Pass exclude rules in if we have them
        if ($this->get_exclude_string()) {
            $command[] = '-x ' . $this->get_exclude_string();
        }
        $command = implode(' ', $command);
        $process = new Process($command);
        $process->setTimeout(HOUR_IN_SECONDS);
        try {
            $process->run();
        } catch (\Exception $e) {
            $this->error(__CLASS__, $e->getMessage());
        }
        if (!$process->isSuccessful()) {
            /**
             * Exit Code 18 is returned when an unreadable file is encountered during the zip process.
             *
             * Given the zip process still completes correctly and the unreadable file is simple skipped
             * we don't want to treat 18 as an actual error.
             */
            if ($process->getExitCode() !== 18) {
                $this->error(__CLASS__, $process->getErrorOutput());
            }
        }
        return $this->verify_backup();
    }