Codeigniter , PHP – form validation only letter in other language?

In Codeigniter 3 I use alpha to validate form for only letters

$this->form_validation->set_rules('firstname', 'FirstName', 'trim|required|alpha',
                array('required' => 'please refill', 'alpha' => 'don't want integer')
            );

but the problem is the Thai Language letter is not work T_T(it’s work only for English letter). I have already put a meta charset utf-8 on head section, but it’s not work too. How should I do?

Answer

As one of the solution you can use the regex_match rule and specify allowed characters. Or you can override the alpha rule and implement it with help of preg_match function. Check the Extending Native Libraries section of the CodeIgniter docs.

Also you can try to play with locales. The alpha rule is implemented using the ctype_alpha function. According to the docs, by default, it uses the standard C locale([A-Za-z]). You can try to change locale using the setlocale function.