Error Displaying in APS Package or validating an entered field

Sample code

$str = “<?xml version=’1.0′ encoding=’UTF-8′?>”;
$str.= ‘<output xmlns=”http://apstandard.com/ns/1/configure-output”><settings>’;
$errorMessages=”mydoubts.in already exists”;
$errsetting=’domainname’;
$str .= ‘<errors>’;
$str .= ‘<error id=”‘.$errsetting.'” setting-id=”‘.$errsetting.'”>’;
$str .= ‘<message>’.$errorMessages.'</message><system>’.$errorMessages.'</system></error>’;
$str .= ‘</errors>’;
$str .= ‘</settings>’;

echo $str;