Solution for $_POST empty after drupal_http_request

The function drupal_http_request can be used to POST data to a URL. However, what the documentation does not mention is that when you invoke it without the Content-Type header, the receiver might not see any of the posted content.

Wrong:

  $result = drupal_http_request(
    url('some/url', array(absolute => TRUE)),
    array(),
    'POST',
    'param1=value1&param2=value2');

Correct:

  $result = drupal_http_request(
    url('some/url', array(absolute => TRUE)),
    array('Content-Type' => 'application/x-www-form-urlencoded'),
    'POST',
    'param1=value1&param2=value2');