Running backup command with phar command doesn't work

[aembler]

I received this error when I attempted to run the backup command on a site:

/usr/share/concretecms-console/concrete.phar backup:backup  --dir=/home/testto_hceu_o2qg/backups/ --instance=/home/testto_hceu_o2qg/public_html/
PHP Fatal error:  Declaration of Symfony\Component\Console\Output\NullOutput::write($messages, bool $newline = false, int $options = self::OUTPUT_NORMAL) must be compatible with Symfony\Component\Console\Output\OutputInterface::write($messages, $newline = false, $options = 0) in /usr/share/concretecms/concrete-cms-9.1.1/concrete/vendor/symfony/console/Output/NullOutput.php on line 124
Whoops\Exception\ErrorException: Declaration of Symfony\Component\Console\Output\NullOutput::write($messages, bool $newline = false, int $options = self::OUTPUT_NORMAL) must be compatible with Symfony\Component\Console\Output\OutputInterface::write($messages, $newline = false, $options = 0) in file /usr/share/concretecms/concrete-cms-9.1.1/concrete/vendor/symfony/console/Output/NullOutput.php on line 124
Stack trace:
  1. Whoops\Exception\ErrorException->() /usr/share/concretecms/concrete-cms-9.1.1/concrete/vendor/symfony/console/Output/NullOutput.php:124
   | array(1) {
   |   [0]=>
   |   string(258) "Declaration of Symfony\Component\Console\Output\NullOutput::write($messages, bool $newline = false, int $options = self::OUTPUT_NORMAL) must be compatible with Symfony\Component\Console\Output\OutputInterface::write($messages, $newline = false, $options = 0)"
   | }

  2. Whoops\Run->handleError() /usr/share/concretecms/concrete-cms-9.1.1/concrete/vendor/filp/whoops/src/Whoops/Run.php:486
   | array(0) {
   | }

  3. Whoops\Run->handleShutdown() [internal]:0
   | array(0) {
   | }

[dimger]

@aembler i had the same issue on a 9.1.1 project. The fix was to update "mnapoli/silly": "^1.7" to "mnapoli/silly": "^1.8" in composer.json. (because of symfony/console dependency conflict)