composer require spatie/laravel-backup

php artisan vendor:publish --provider="SpatieBackupBackupServiceProvider"

<?php

'backup' => [

    /*
     * The name of this application. You can use this name to monitor
     * the backups.
     */
    'name' => config('app.name'),

    'source' => [

        'files' => [

            /*
             * The list of directories and files that will be included in the backup.
             */
            'include' => [
                base_path(),
            ],

            /*
             * These directories and files will be excluded from the backup.
             *
             * Directories used by the backup process will automatically be excluded.
             */
            'exclude' => [
                base_path('vendor'),
                base_path('node_modules'),
            ],

            /*
             * Determines if symlinks should be followed.
             */
            'followLinks' => false,
        ],

        /*
         * The names of the connections to the databases that should be backed up
         * MySQL, PostgreSQL, SQLite and Mongo databases are supported.
         */
        'databases' => [
            'mysql',
        ],
    ],

    /*
     * The database dump can be gzipped to decrease diskspace usage.
     */
    'gzip_database_dump' => false,

    'destination' => [

        /*
         * The filename prefix used for the backup zip file.
         */
        'filename_prefix' => '',

        /*
         * The disk names on which the backups will be stored.
         */
        'disks' => [
            'local',
        ],
    ],

    /*
     * The directory where the temporary files will be stored.
     */
    'temporary_directory' => storage_path('app/backup-temp'),
],

/*
 * You can get notified when specific events occur. Out of the box you can use 'mail' and 'slack'.
 * For Slack you need to install guzzlehttp/guzzle.
 *
 * You can also use your own notification classes, just make sure the class is named after one of
 * the `SpatieBackupEvents` classes.
 */
'notifications' => [

    'notifications' => [
        SpatieBackupNotificationsNotificationsBackupHasFailed::class         => ['mail'],
        SpatieBackupNotificationsNotificationsUnhealthyBackupWasFound::class => ['mail'],
        SpatieBackupNotificationsNotificationsCleanupHasFailed::class        => ['mail'],
        SpatieBackupNotificationsNotificationsBackupWasSuccessful::class     => ['mail'],
        SpatieBackupNotificationsNotificationsHealthyBackupWasFound::class   => ['mail'],
        SpatieBackupNotificationsNotificationsCleanupWasSuccessful::class    => ['mail'],
    ],

    /*
     * Here you can specify the notifiable to which the notifications should be sent. The default
     * notifiable will use the variables specified in this config file.
     */
    'notifiable' => SpatieBackupNotificationsNotifiable::class,

    'mail' => [
        'to' => 'your@example.com',
    ],

    'slack' => [
        'webhook_url' => '',

        /*
         * If this is set to null the default channel of the webhook will be used.
         */
        'channel' => null,

        'username' => null,

        'icon' => null,

    ],
],

/*
 * Here you can specify which backups should be monitored.
 * If a backup does not meet the specified requirements the
 * UnHealthyBackupWasFound event will be fired.
 */
'monitorBackups' => [
    [
        'name' => config('app.name'),
        'disks' => ['local'],
        'newestBackupsShouldNotBeOlderThanDays' => 1,
        'storageUsedMayNotBeHigherThanMegabytes' => 5000,
    ],

    /*
    [
        'name' => 'name of the second app',
        'disks' => ['local', 's3'],
        'newestBackupsShouldNotBeOlderThanDays' => 1,
        'storageUsedMayNotBeHigherThanMegabytes' => 5000,
    ],
    */
],

'cleanup' => [
    /*
     * The strategy that will be used to cleanup old backups. The default strategy
     * will keep all backups for a certain amount of days. After that period only
     * a daily backup will be kept. After that period only weekly backups will
     * be kept and so on.
     *
     * No matter how you configure it the default strategy will never
     * delete the newest backup.
     */
    'strategy' => SpatieBackupTasksCleanupStrategiesDefaultStrategy::class,

    'defaultStrategy' => [

        /*
         * The number of days for which backups must be kept.
         */
        'keepAllBackupsForDays' => 7,

        /*
         * The number of days for which daily backups must be kept.
         */
        'keepDailyBackupsForDays' => 16,

        /*
         * The number of weeks for which one weekly backup must be kept.
         */
        'keepWeeklyBackupsForWeeks' => 8,

        /*
         * The number of months for which one monthly backup must be kept.
         */
        'keepMonthlyBackupsForMonths' => 4,

        /*
         * The number of years for which one yearly backup must be kept.
         */
        'keepYearlyBackupsForYears' => 2,

        /*
         * After cleaning up the backups remove the oldest backup until
         * this amount of megabytes has been reached.
         */
        'deleteOldestBackupsWhenUsingMoreMegabytesThan' => 5000,
    ],
],

php artisan backup:run

Starting backup...
In BackupDestination.php line 138:
Parse error: syntax error, unexpected '?'