createBackupFile example

$destination = $this->pluginDir;

        if (!is_writable($destination)) {
            throw new Exception(sprintf('Destination directory "%s" is not writable', $destination));
        }

        $prefix = $this->getPluginPrefix($archive);
        $this->validatePluginZip($prefix, $archive);
        $this->validatePluginRequirements($prefix, $archive);

        $oldFile = $this->findOldFile($prefix);
        $backupFile = $this->createBackupFile($oldFile);

        try {
            $archive->extractTo($destination);

            if ($backupFile !== false) {
                $this->filesystem->remove($backupFile);
            }

            unlink($archive->filename);
        } catch (Exception $e) {
            if ($oldFile !== false) {
                

$destination = $this->extensionDirectories[$type];

        if (!is_writable($destination)) {
            throw new PluginExtractionException(sprintf('Destination directory "%s" is not writable', $destination));
        }

        $pluginName = $this->getPluginName($archive);
        $this->validatePluginZip($pluginName, $archive);

        $oldFile = $this->findOldFile($destination, $pluginName);
        $backupFile = $this->createBackupFile($oldFile);

        try {
            $archive->extractTo($destination);

            if ($backupFile !== null) {
                $this->filesystem->remove($backupFile);
            }

            if ($delete) {
                unlink($archive->filename);
            }
        }