如何创建RESTful API？

Question

Over the last few weeks I've been learning about iOS development, which has naturally led me into the world of APIs. Now, searching around on the Internet, I've come to the conclusion that using the REST architecture is very much recommended, due to its supposed simplicity and ease of implementation.

However, I'm really struggling with the implementation side of REST. I understand the concept; using HTTP methods as verbs to describe the action of a request and responding with suitable response codes, and so on. It's just, I don't understand how to code it.

I don't get how I map a URI to an object. I understand that a GET request for domain.com/api/user/address?user_id=999 would return the address of user 999 - but I don't understand where or how that mapping from /user/address to some method that queries a database has taken place.

Is this all coded in one PHP script? Would I just have a method that grabs the URI like so:

$array = explode("/", ltrim(rtrim($_SERVER['REQUEST_URI'], "/"), "/"))

And then cycle through that array, first I would have a request for a "user", so the PHP script would direct my request to the user object and then invoke the address method. Is that what actually happens?

The main thing I'm not getting is how that URI /user/address?id=999 somehow is broken down and executed - does it actually resolve to code?

class user(id) {
   address() {
     //get user address
   }
}

Answer 1

That's two questions.

To honor RESTful HTTP verbs, you have to query $_SERVER["REQUEST_METHOD"] . It will contain the usual GET or POST unless a more specialized HTTP request was received. The whole REST buzz is somewhat misleading in itself, and also in misusing the HTTP verbs just for routing.

Anyway, the mapping of request URLs to functions can be achieved in two ways. It's most reliable to use a static map, for example an array that lists URL patterns and destination methods. Most PHP frameworks use an implicit mapping like so:

$args = explode("/", trim($_SERVER['REQUEST_URI'], "/"));
$class = array_shift($args);
$method = array_shift($args);
call_user_func_array("$class::$method", $args);

Note how this is a bad example, security-wise. Only allowed and specifically prepared classes and methods should be able to receive requests. Most frameworks just check if it was derived from an acceptable base class after loading it from a known path and/or instantiating. But a static map is really preferable.

Anyway, regular expression mapping or handling by mod_rewrite is also common. And for utilizing HTTP verbs, just include it as method name.

Answer 2

Actually the API you're trying to describe now is not RESTful . There are many sources describing how to make RESTful APIs. So you should first define your API (taking in account how your client software would use it) and then implement it. I'm quite sure that almost any RESTful API can be implemented in PHP.

Here are some other tips on how to make a RESTful API.

In my opinion GlassFish Server REST Interface is a good example of RESTful design.

Answer 3

Have a look at FRAPI - http://getfrapi.com/

As it says focus on your business logic, not presentation.