【Composer】Your requirements could not be resolvedエラーの対処法

PHP

2022.09.05

Composerでパッケージをインストールしようとしたところ、

composer require laravel/fortify

次のようなエラーが発生しました。

Your requirements could not be resolved to an installable set of packages.

>composer require laravel/fortify
./composer.json has been updated
Running composer update laravel/fortify
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - Root composer.json requires laravel/fortify 1.11 -> satisfiable by laravel/fortify[v1.11.0].
    - laravel/fortify v1.11.0 requires illuminate/support ^8.82|^9.0 -> found illuminate/support[v8.82.0, ..., 8.x-dev, v9.0.0-beta.1, ..., 9.x-dev] but these were not loaded, likely because it conflicts with another require.


Installation failed, reverting ./composer.json and ./composer.lock to their original content.

このエラーの対処法をメモしておきます。