polylang add flags and names to header.php

I am using following code for displaying languages flag and their names in my website header. I wrote this code in header.php, but using this code only display languages in one page not in other pages. I have two languages: English and Swedish. In English page flags are not showing while in Swedish page flags are shown. Can anybody throw light on this.
<ul id="ul_lang"><?php pll_the_languages(array('show_flags'=>1,'show_names'=>1));?></ul>