Creating a simple REST client

REST clients use HyperText Transfer Protocol (HTTP) to generate requests to external web services. By changing the HTTP method, we can cause the external service to perform different operations. Although there are quite a few methods (or verbs) available, we will only focus on GET and POST. In this recipe, we will use the Adapter software design pattern to present two different ways of implementing a REST client.

How to do it...

1. Before we can define REST client adapters, we need to define common classes to represent request and response information. First, we will start with an abstract class that has methods and properties needed for either a request or response:

   namespace Application\Web;
   
   class AbstractHttp
   {

2. Next, we define class constants that represent HTTP information:

   const METHOD_GET = 'GET';
   const METHOD_POST = 'POST';
   const METHOD_PUT = 'PUT';
   const METHOD_DELETE = 'DELETE';
   const CONTENT_TYPE_HTML = 'text/html';
   const CONTENT_TYPE_JSON = 'application...