herokuへのデプロイ時のエラー

Question

前提・実現したいこと

git push heroku master のコマンド実行時にエラーが生じました。
これを解決したいです。

https://www.hypertextcandy.com/laravel-tutorial-deploy-to-heroku
これが参考にしたサイトです。

発生している問題・エラーメッセージ

remote:        Script @php artisan package:discover --ansi handling the post-autoload-dump event returned with error code 255
remote:  !     WARNING: A post-autoload-dump script terminated with an error
remote:
remote:  !     ERROR: Dependency installation failed!
remote:  !
remote:  !     The 'composer install' process failed with an error. The cause
remote:  !     may be the download or installation of packages, or a pre- or
remote:  !     post-install hook (e.g. a 'post-install-cmd' item in 'scripts')
remote:  !     in your 'composer.json'.
remote:  !
remote:  !     Typical error cases are out-of-date or missing parts of code,
remote:  !     timeouts when making external connections, or memory limits.
remote:  !
remote:  !     Check the above error output closely to determine the cause of
remote:  !     the problem, ensure the code you're pushing is functioning
remote:  !     properly, and that all local changes are committed correctly.
remote:  !
remote:  !     For more information on builds for PHP on Heroku, refer to
remote:  !     https://devcenter.heroku.com/articles/php-support
remote:  !
remote:  !     REMINDER: the following warnings were emitted during the build;
remote:  !     check the details above, as they may be related to this error:
remote:  !     - A post-autoload-dump script terminated with an error
remote:
remote:  !     Push rejected, failed to compile PHP app.
remote:
remote:  !     Push failed
remote:  !
remote:  ! ## Warning - The same version of this code has already been built: 747f19d95313c0e21daaf2ea9a981e2cd65d37ad
remote:  !
remote:  ! We have detected that you have triggered a build from source code with version 747f19d95313c0e21daaf2ea9a981e2cd65d37ad
remote:  ! at least twice. One common cause of this behavior is attempting to deploy code from a different branch.
remote:  !
remote:  ! If you are developing on a branch and deploying via git you must run:
remote:  !
remote:  !     git push heroku <branchname>:main
remote:  !
remote:  ! This article goes into details on the behavior:
remote:  !   https://devcenter.heroku.com/articles/duplicate-build-version
remote:
remote: Verifying deploy...
remote:
remote: !       Push rejected to damp-fjord-29872.
remote:
To https://git.heroku.com/damp-fjord-29872.git
 ! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/damp-fjord-29872.git'

composer.json

{
    "name": "laravel/laravel",
    "type": "project",
    "description": "The Laravel Framework.",
    "keywords": [
        "framework",
        "laravel"
    ],
    "license": "MIT",
    "require": {
        "php": "^7.2.5|^8.0",
        "fideloper/proxy": "^4.4",
        "fruitcake/laravel-cors": "^2.0",
        "guzzlehttp/guzzle": "^6.3.1|^7.0.1",
        "laravel/framework": "^7.29",
        "laravel/tinker": "^2.5",
        "laravel/ui": "2.5"
    },
    "require-dev": {
        "facade/ignition": "^2.0",
        "fakerphp/faker": "^1.9.1",
        "mockery/mockery": "^1.3.1",
        "nunomaduro/collision": "^4.3",
        "phpunit/phpunit": "^8.5.8|^9.3.3"
    },
    "config": {
        "optimize-autoloader": true,
        "preferred-install": "dist",
        "sort-packages": true
    },
    "extra": {
        "laravel": {
            "dont-discover": []
        }
    },
    "autoload": {
        "psr-4": {
            "App\": "app/"
        },
        "classmap": [
            "database/seeds",
            "database/factories"
        ]
    },
    "autoload-dev": {
        "psr-4": {
            "Tests\": "tests/"
        }
    },
    "minimum-stability": "dev",
    "prefer-stable": true,
    "scripts": {
        "post-autoload-dump": [
            "Illuminate\Foundation\ComposerScripts::postAutoloadDump",
            "@php artisan package:discover --ansi"
        ],
        "post-root-package-install": [
            "@php -r \"file_exists('.env') || copy('.env.example', '.env');\""
        ],
        "post-create-project-cmd": [
            "@php artisan key:generate --ansi"
        ]
    }
}

試したこと

このエラーコードについて調べたらいろんな記事が出てきたんですが、どの記事も解決できなかったので、質問しました。
ためしたサイト
https://stackoverflow.com/questions/64456175/a-post-autoload-dump-script-terminated-with-an-error
https://teratail.com/questions/175530
https://www.webune.com/forums/axpxyr.html
https://teratail.com/questions/175530
https://qiita.com/gotokoki1/items/788f97b18dfe9ab78d1c
https://www.fixes.pub/program/254687.html

補足情報（FW/ツールのバージョンなど）

PHP 7.4.26
laravel 7.30.1
virtualbox バージョン 6.1.28
centos-8
laravel/ui 2.5

Answer 1

https://devcenter.heroku.com/changelog-items/2304
このサイト見てHerokuのPHPが8.1に上がったせいでpushに失敗するらしく、
PHPのバージョンが8.0以上じゃないといけないと書いてあって、
https://blog.apar.jp/php/14976/
このサイトでバージョンをアップデートしたら、できるようになりました。

Comments

[work1212]

composer.jsonのphpの部分も8.0.0にしてコマンドでcomposer updateしました。