Make a HTTP Request in Salesforce

We can make http request in salesforce. We must define a remote site of it before making a http request.

Add site in remote site setting :
Go in the Setup Menu -->Administer ---> Remote Site Settings ---> Add here your site setting

String payLoad = 'some_data=value+1&some_more_data=value+2&etc_etc';
Http h = new Http();
HttpRequest req = new HttpRequest();
req.setEndpoint('http://www.contoso.com/');
req.setMethod('POST');
req.setBody(payLoad);
HttpResponse res = h.send(req);

system.debug(‘Response :’+res.getBody());