status code 200 in response of web service + XCode

I am getting status code 200 in response of web service request. And getting nil data at time of serialization using [NSJSONSerialization JSONObjectWithData:data options:0 error:&error]

But this web service is working properly on Google chrome's Postman.
Can anybody tell me why is it not working in code ?

Response of my web service (Post method):

<NSHTTPURLResponse: 0x7fda63c82810> { URL: http://example.com/iphone/webservice.php?action=pagination } { status code: 200, headers {
Connection = "Keep-Alive";
"Content-Type" = "text/html";
Date = "Wed, 04 Nov 2015 06:11:30 GMT";
"Keep-Alive" = "timeout=5, max=100";
Server = "Apache/2.2.27 (Unix) mod_ssl/2.2.27 OpenSSL/1.0.1e-fips";
"Transfer-Encoding" = Identity;
"X-Powered-By" = "PHP/5.4.27";
} 

}

Thanks in advance