How to create language object from language string (e.g. 'en')? As in question, ofcourse I am asking about Drupal function for this job. 

So I need function that get language string as param (e.g 'en','pl' etc) and returns me standard Drupal language object. Similar to global $language.
Use language_list() function:

&lt;?php

function get_langugage_object($language) {
  $installed_languages = language_list();
  return $installed_languages[$language];
}

?&gt;