herokuでデプロイ中、pushするとエラーが吐かれる。

現在こちらのサイトを参考にherokuでデプロイを行っております。環境設定などが終わり、いざgit push heroku masterこのコマンドでpushを行うと下記のようなエラーメッセージが吐かれます。

remote: Compressing source files... done.

remote: Building source:
remote:
remote: -----> Building on the Heroku-20 stack
remote: -----> PHP app detected
remote:
remote: ! ERROR: Basic validation for 'composer.json' failed!
remote: !
remote: ! It must be a valid JSON document compatible with Composer.
remote: !
remote: ! You most likely created or edited the file by hand, and it now
remote: ! contains a syntax error. Please refer to the documentation at
remote: ! https://getcomposer.org/doc/ for information on the format.
remote: !
remote: ! You can run 'composer validate' locally on your computer for
remote: ! further diagnosis. Remember to also always keep your lock file
remote: ! up to date with any changes according to the instructions at
remote: ! https://getcomposer.org/doc/01-basic-usage.md
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: dc44b8d11d86802a1f6dca2a9d7be45590937441
remote: !
remote: ! We have detected that you have triggered a build from source code with version dc44b8d11d86802a1f6dca2a9d7be45590937441
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 peaceful-savannah-45671.
remote:
To https://git.heroku.com/peaceful-savannah-45671.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/peaceful-savannah-45671.git'