On the Codevate.com blog there's a tutorial posted by Chris Lush showing you how to secure your client-side public API with OAuth 2 (based on the Symfony platform).

Say you’ll be developing a web application for a customer to create and manage restaurant bookings, exposing restaurant information (name, opening times, menu contents etc.) and booking creation as RESTful API endpoints, which are consumed by secure admin backend. You’ll need to authorise access to the API, but there is no end-user involved since the web app is its own resource owner, so the previous flow doesn’t apply.

[...] However, you also need to develop a booking widget that will be embedded in a company or restaurant’s website for visitors to use. In this case, the client-side is no longer trusted enough to share the OAuth client secret that’s required to authenticate with your API. [...] We encountered a similar use-case for a client project recently, and this blog post details the steps taken to address it.

He then shows how to integrate the FOSOAuthServerBundle bundle into your current Symfony-based application and the updates you'll need to make to your security.yml file. He includes the code needed to create a "client" and associating it with a company already in the customer list. Next is the creation of access tokens and linking them to the restaurants in their system (a unique identifier to use externally for the restaurant rather than an ID). He shows an example of handling the token requests and the code/config changes needed to set it up. Finally he talks about scoping API requests down to certain functionality and an example cURL call to the API to show the results of it all combined.