Laravel 4.2 Symfony错误（未找到'Symfony \ Component \ Translation \ TranslatorInterface'）

I am currently running an old version of laravel project 4.2 and I get the following error.

Symfony \ Component \ Debug \ Exception \ FatalErrorException Interface 'Symfony\Component\Translation\TranslatorInterface' not found

any help I will really appreciate

composer update
composer dump-autoload

It's possible that the version is so old that you can't load that package. So you should update to a newer version for security reasons it a good choice. Take a migration guide and try it.

And you have tagged your question with "PHP 7.1" i don't think that version 4.2 is compatible with that version and can cause problems.