• Web Service
  • It's based on SOAP and returns data in XML form.
  • It supports only HTTP protocol.
  • It is not open source but can be consumed by any client that understands xml.
  • It can be hosted only on IIS.
• WCF
  • It is also based on SOAP and returns data in XML form.
  • It is the evolution of the web service(ASMX) and supports various protocols like TCP, HTTP, HTTPS, Named Pipes, MSMQ.
  • The main issue with WCF is it's tedious and extensive configuration.
  • It is not open source but can be consumed by any client that understands xml.
  • It can be hosted with in the applicaion or on IIS or using window service.
• WCF Rest
  • To use WCF as WCF Rest service you have to enable webHttpBindings.
  • It support HTTP GET and POST verbs by [WebGet] and [WebInvoke] attributes respectively.
  • To enable other HTTP verbs you have to do some configuration in IIS to accept request of that particular verb on .svc files
  • Passing data through parameters using a WebGet needs configuration. The UriTemplate must be specified
  • It support XML, JSON and ATOM data format.
• Web API
  • This is the new framework for building HTTP services with easy and simple way.
  • Web API is open source an ideal platform for building REST-ful services over the .NET Framework.
  • Unlike WCF Rest service, it use the full featues of HTTP (like URIs, request/response headers, caching, versioning, various content formats)
  • It also supports the MVC features such as routing, controllers, action results, filter, model binders, IOC container or dependency injection, unit testing - all of which makes it more simple and robust.
  • It can be hosted with in the application or on IIS.
  • It has a lightweight architecture and is good for devices which have limited bandwidth like smart phones.
  • Responses are formatted by Web API's MediaTypeFormatter into JSON, XML or whatever format you want to add as a MediaTypeFormatter.

• Choose WCF when you want to create a service that should support special scenarios such as one way messaging, message queues, duplex communication etc.
• Choose WCF when you want to create a service that can use fast transport channels when available, such as TCP, Named Pipes, or maybe even UDP (in WCF 4.5), and you also want to support HTTP when all other transport channels are unavailable.
• Choose Web API when you want to create a resource-oriented services over HTTP that can use the full features of HTTP (like URIs, request/response headers, caching, versioning, various content formats).
• Choose Web API when you want to expose your service to a broad range of clients including browsers, mobiles, iphone and tablets. (dotnettricks)

class Spreadsheet {
     public $name; //here's your property
     function __construct() {          
     $this->name="Bruce"; //here's your constructor giving the value "Bruce" to your "name" property          
     echo $this->name;     
     }
}
$new_spreadsheet = new Spreadsheet();

When you run this code, you'll get "Bruce."

Global variables are accessible from any class, method or function from anywhere in the application. Public, Private, Protected, Child, Parent - doesn't matter. If it's a Superglobal variable, you can grab it and use it and you only have to define it once.

An example would be $_SESSION. That's considered a Superglobal variable in that PHP knows what $_SESSION is. You still have to give it a value, but you don't have to "define" $_SESSION anymore than you have to "define" $_POST or $_GET. PHP knows what those variables are. Again, you still have to give them a value, but systemically, PHP is not looking for that variable, it already knows what it is.

You have the same kind of utility available to you with a "Global" variable, but, unlike a Superglobal variable, you have to define it. Whereas $_SESSION is understood by PHP, $george, on the other hand, is a total mystery.

$george could be your database connection, but in order to give it "wings" so it can fly freely throughout your app, you have to make it a global variable like this:

Here's your database connection script:

$mysqli = new mysqli($host,$user,$password,$database);
if($mysqli->connect_errno) {  
$err="CONNECT FAIL: "  
.$mysqli->connect_errno  
. ' '  
.$mysqli->connect_error  ;  
trigger_error($err, E_USER_ERROR);
}

Now here's my class:

class List {
 
     public spreadsheet () {
          global $mysqli;
          $sql="select * from table";
          $query=$mysqli->query($sql);

     }

}

I've just told my code to go look for $mysqli. It could be anywhere, but by prefacing $mysqli with "global," I'm giving my code permission to go and look anywhere and everywhere for the $mysqli variable.