Question

I have installed composer from this link, but I still could not find where do I need to place the composer.json file.

Answer 1

In the root of your project. Because you mentioned symfony, just have a look at the composer.json from the symfony-standard edition

https://github.com/symfony/symfony-standard/

Or even better: Follow the official instructions and use symfony-standard as starting point for your project directly.

Start by visiting the Symfony2 download page at http://symfony.com/download. On this page, you’ll see the Symfony Standard Edition, which is the main Symfony2 distribution.

You can forkt it directly from github.