problems with strtolower function

have your tried using mb_strtolower()?

PHP5 is not UTF-8 compatible, so you still need to resort to the mb extension. I suggest you set the internal encoding of mb to utf-8 and then you can freely use its functions without specifying the charset all the time:

mb_internal_encoding('UTF-8');

...

$b = mb_strtolower($a);
echo $b;

i have found this solution from here

$string = 'Թ';
echo 'Uppercase: '.mb_convert_case($string, MB_CASE_UPPER, "UTF-8").'';
echo 'Lowercase: '.mb_convert_case($string, MB_CASE_LOWER, "UTF-8").'';
echo 'Original: '.$string.'';

works for me (lower case)