Failed to detect set buildpack https://codon-buildpacks.s3.amazonaws.com/buildpacks/heroku/php.tgz

It appears that you are trying to deploy a static website to Heroku but specifying the heroku/php builpack which expects, well… a PHP app.

Two possible ways of doing this:

Meet the requirements of the heroku/php webpack:

1. Have some PHP code. For example, an index.php file with a redirect, like:

   <?php header( 'Location: /index.html' ) ; ?>

2. Have a composer.json file, which can just be:

   {}

Use heroku-buildpack-static:

This is a custom webpack for serving static sites. A complete guide is available here, but the highlights are:

heroku plugins:install heroku-cli-static
heroku buildpacks:set https://github.com/hone/heroku-buildpack-static
heroku static:init
heroku static:deploy