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The problem is that you require doctrine/common in v2. This depends on doctrine/persistence in v1. Updating all your packages to Symfony 5.2 will also update symfony/doctrine-bridge to 5.2 - and this requires doctrine/persistence in v2.

Updating doctrine/common to v3 in your composer.json could help to resolve the problem. Also, since you are using symfony/flex already, you can remove all explicit version constraints on the Symfony packages - it's sufficient to define the Symfony version further down in the extra section as you already did. This makes it way easier to update all Symfony packages, as you only need to change this one line

That composer.json file is a bit of a mess. Some Symfony packages on 5.3, some even on 5.1, and many on 6.

Also you are controlling Symfony versioning from extra.symfony.require, and at the same time from the discrete version constraints. You include some packages that no longer exist on 6.0 (symfony/security-guard), and are missing some that should be installed on a 6.0 version.

It's simply not on an installable state.

I've managed to make it installable changing it like this:

Try changing composer.json

From:

The solution is to execute:

You have conflicting requirements.

On extra.symfony.require you say you want 5.3.*.

But on your individual Symfony requirements you are specifying either ^5.2 or 5.2.* (and in some cases ^5.3 as well).

When a project uses Symfony Flex (as is your case), the presence of extra.symfony.require will be used to restrict what package versions to install for many/most Symfony packages. But only if you do not declare a specific version on your require section.

In this case, you are already specifying a version on the 5.* range on extra.symfony.require. Leave that one like that, and just use * as a version constraint for all the other Symfony Packages in the require section.

(Note that's it's not really all, since some packages are not managed by Flex, just update the ones that have versions declares in the 5.* range)

As you can read in an issue posted in the issue tracker of doctrine/cache, that class has been deprecated in v1 of that package, and removed in v2.

If you still want to use that class, run composer require doctrine/cache "^1.12" to install a version of that package from the v1 branch.

On the long run, you should check where your application requires that class and search for alternatives. If you need help with that, please share more details.

You have two problems:

• You have Symfony '5.3' installed, which was released just one day ago.
• You are using PHP 8, which is not supported by Sylius. By using PHP 8, you end up installing versions of dependencies that are not compatible with Sylius.

Since the current version of Sylius supports up to 5.2, and PHP ^7.3, you'll have to either downgrade to Sf 5.2 and PHP >= 7.3 && PHP < 8, or wait a some time so support for Sf 5.3 and PHP >= 8 is baked in.

I would recommend using the standard Sylius installation, but trying to install Sylius with the recommended docs way (composer create-project sylius/sylius-standard acme) when using PHP 8 also fails. But downgrading to PHP 7.4 and running the create-project command does work.

The project seems to have entered the dependency hell stage of development.

Considering your output:

Restricting packages listed in "symfony/symfony" to "5.0.*"

You currently have something like this in your composer.json:

stof/doctrine-extensions-bundle v1.6.0 requires symfony/http-kernel ^4.4 || ^5.2 looks pretty clear to me: that package in that given version is not compatible with Symfony 5.0

Either downgrade stof/doctrine-extensions-bundle to v1.5 (which is compatible with Symfony 5.0), or (the better solution) update Symfony to v5.2 - the Support for 5.0 has ended in July 2020