PHP アプリを Cloud9 から Heroku にプッシュすると、アプリケーションが Heroku にデプロイされます。問題は、将来、バグ修正や更新などを行う必要がある場合、Heroku でホスト/デプロイされているアプリケーションを編集できるようになるかどうかです。
編集：
zeldish:~/workspace/appzeld (master) $ git push heroku master
Counting objects: 3, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (3/3), done.
Writing objects: 100% (3/3), 381 bytes | 0 bytes/s, done.
Total 3 (delta 2), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Using set buildpack heroku/php
remote: -----> PHP app detected
remote:
remote: ! WARNING: No 'composer.json' found.
remote: Using 'index.php' to declare app type as PHP is considered legacy
remote: functionality and may lead to unexpected behavior.
remote:
remote: -----> Bootstrapping...
remote: -----> Installing platform packages...
remote: NOTICE: No runtime required in composer.lock; using PHP ^5.5.17
remote: - apache (2.4.20)
remote: - nginx (1.8.1)
remote: - php (5.6.22)
remote: -----> Installing dependencies...
remote: Composer version 1.1.2 2016-05-31 19:48:11
remote: -----> Preparing runtime environment...
remote: NOTICE: No Procfile, using 'web: vendor/bin/heroku-php-apache2'.
remote: -----> Checking for additional extensions to install...
remote:
remote: -----> Discovering process types
remote: Procfile declares types -> web
remote:
remote: -----> Compressing...
remote: Done: 13.9M
remote: -----> Launching...
remote: Released v4
remote: https://*******.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/********.git
59f63a5..4375225 master -> master