symfony

As all the php vhost templates, the symfony template first takes care of having the basic php support.

Then, let's take a look at the custom variables:

HTTP_ENV="dev" # For symfony, set the value for $APP_ENV when using http
HTTPS_ENV="prod" # For symfony, set the value for $APP_ENV when using https

# Index setting. If empty, defaults to index.php. For old symfony versions, set to app.php
INDEX_BLOCK=""

When running under a web server, symfony uses the APP_ENV variable to set the running environment (matching the same setting in .env files). For granularity, if you wish to have different environments in http and https, you can choose different values for HTTP_ENV and HTTPS_ENV.

For old versions (<4), the document root was in the "web" directory (later it's "public"), and the index setting should be app.php. So, if left empty, the INDEX_BLOCK variable defaults to index.php.