Which API standard?

We're planning a new project which will feature an API available to customers to interact with our app from their own web sites and 开发者_如何学Csystems. However never having built anything close to an full-fledged API in the past, I am not aware of any standards or recommendations that are available and could be used to make the API more easily adapted by our customers.

We will build the API using PHP and some parts of the API will need authentication while others don't. As of today, I have read a little about Oauth, SOAP & REST, but I have no idea on what is good practiec.

What technology/standard is recommended to base an API for 2011+ upon?

There are a number of options, but I would suggest that you may find publishing a SOAP API from PHP quite tricky to maintain.

The reason for this is that there is no inherent WSDL generation within PHP, so you'll either have to roll your own (and modify it each time), or experiment with one of the 3rd party tools - none of which I have found particularly satisfactory in the past.

I would suggest that a more straightfoward method for implementing an API in PHP would be to go down the RESTful route.

I would check out the choices made by successful APIs that are available through sites like Mashery or Programmable Web. By focusing on the successful API patterns before choosing a technology you will have a better chance that the API will work and be successful.