Several fatal errors showed up during the upgrade to Magento 2.3.5 from 2.3.4 which, after research, were found to have been caused by the outdated version of composer. Running composer self-update unfortunately doesn't work. Is there a different command or an approach to updating composer to its latest version?

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2 Answers 2


I have successfully upgrade my composer version using composer composer self-update

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What issue you are facing.

  • This message is what I see when running composer self-update is run. Command "self-update" is not defined. Jun 6, 2020 at 5:11
  • can you please share your screenshot when run command and error message Jun 6, 2020 at 5:21
  • Added screenshot showing part of the error messages that I get. thanks for your assistance. Jun 6, 2020 at 5:26

What about if you try and reinstall composer

php -r "copy('https://getcomposer.org/installer', 'composer-setup.php');"
php -r "if (hash_file('sha384', 'composer-setup.php') === 'e0012edf3e80b6978849f5eff0d4b4e4c79ff1609dd1e613307e16318854d24ae64f26d17af3ef0bf7cfb710ca74755a') { echo 'Installer verified'; } else { echo 'Installer corrupt'; unlink('composer-setup.php'); } echo PHP_EOL;"
php composer-setup.php
php -r "unlink('composer-setup.php');"

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