Access-Control-Allow-Origin is not showing up in response headers from codeigniter

Question

My Codeigniter file says

$CI->output->set_header("Access-Control-Allow-Origin: *");
$CI->output->set_header("Access-Control-Expose-Headers: Access-Control-Allow-Origin");
$CI->output->set_status_header(200);
$CI->output->set_content_type('application/json');
echo json_encode(array("city" => "dhaka"));

but the http response that i get are:

Request URL:http://localhost/index.php/location/city
Request Method:POST
Status Code:200 OK

Connection:Keep-Alive
Content-Length:16
Content-Type:text/html
Date:Sun, 22 Jul 2012 10:27:32 GMT
Keep-Alive:timeout=5, max=100
Server:Apache/2.2.21 (Unix) mod_ssl/2.2.21 OpenSSL/0.9.8r DAV/2 PHP/5.3.6
X-Powered-By:PHP/5.3.6

The header Access-Control-Allow-Origin is missing in the response even after including Access-Control-Expose-Headers: Access-Control-Allow-Origin. My source of information about this header is from Mozilla Developer Website

Solution 1

It turns out, it worked for me only when i set the headers via the PHP syntax header() instead of the codeigniter syntax $CI->output->set_header(). That's sad.

Thanks to the first comment by @Yan at the Question of this topic

Solution 2

If you look closely you can also notice the content-type being different: it's text/html, whereas you are requesting application/json. This happens because while you are preparing the headers correctly, you never actually output them. As far as I know you can do this in at least 2 ways:

1. Use the output library's set_output function to output everything at once.

   $json = json_encode(array("city" => "dhaka"));
   
   $this->output->set_header("Access-Control-Allow-Origin: *");
   $this->output->set_header("Access-Control-Expose-Headers: Access-Control-Allow-Origin");
   $this->output->set_status_header(200);
   $this->output->set_content_type('application/json');
   
   $this->output->set_output($json);
   

2. Call the output-library's _display() function, to first output the correct headers and then append your json object with echo.

   $this->output->set_header("Access-Control-Allow-Origin: *");
   $this->output->set_header("Access-Control-Expose-Headers: Access-Control-Allow-Origin");
   $this->output->set_status_header(200);
   $this->output->set_content_type('application/json');
   $this->output->_display();
   
   echo json_encode(array("city" => "dhaka"));
   

   This function sends the finalized output data to the browser along with any server headers and profile data. (From CI/system/core/Output.php line 316)