You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query>
    <pages>
      <page ns="14" title="Category:Foo" missing="" />
      <page ns="14" title="Category:Bar" missing="" />
    </pages>
  </query>
</api>
Warning: Trying to access array offset on value of type bool in /customers/c/d/0/laage.se/httpd.www/wiki/includes/libs/IPSet.php on line 244 Warning: Trying to access array offset on value of type bool in /customers/c/d/0/laage.se/httpd.www/wiki/includes/libs/IPSet.php on line 247 Warning: Trying to access array offset on value of type bool in /customers/c/d/0/laage.se/httpd.www/wiki/includes/libs/IPSet.php on line 244 Warning: Trying to access array offset on value of type bool in /customers/c/d/0/laage.se/httpd.www/wiki/includes/libs/IPSet.php on line 247