Codeigniter Form Validation - Custom callback with regex that allows accents - php

Question

Before anyone flames me, I'd like to say I have tried all solutions here on SO as well as google but nothing works :(. I need some enlightenment :)
Here is my custom form_validation callback function.
Code Snippet
function _check_valid_text($text_string)
{
if(empty($text_string)) return TRUE;
if(!preg_match("/^[\pL\pN_ \w \-.,()\n]+$/i", $text_string))
{
// Set the error message:
$this->form_validation->set_message('_check_valid_text', 'Invalid Character or symbol');
return FALSE;
}
return TRUE;
}
WHAT I WANT:
Allow all alphanumeric characters [a-z, A-Z & 0-9]
Allow accents
Allow the following too: space, open brace, close brace, dash, period and comma
Strangely
für works, i.e. no error (YAY!).
trägen does not :(
Can someone please tell me where I am going wrong?
PS: Please don't provide solutions where your solution is to include the char that is not getting recognized into the preg_match string (e.g. add ä into the string). I am looking for a generic solution that works.
PPS I want to make a suggestion to the community. How about having a library of regex expressions for various cases? One can write a regex and once someone else verifies that it is working it can be accepted. Just a suggestion though. I assume there are more newcomers here like me who get stuck a lot in regex-hell :)

Answer 1

You must add the u modifier to inform the regex engine that your string must be treated as an unicode string. Note too that you can reduce your character class, example:
$subjects = array('Wer nur den lieben Gott läßt walten',
'Sei gegrüßet Jesu gütig',
'Komm, Gott, Schöpfer, Heiliger Geist',
'←↑→↓');
$pattern = '~^[\pL\pN\s,.()_-]++$~u';
foreach ($subjects as $subject) {
if (preg_match($pattern, $subject, $match))
echo '<br/>True';
else
echo '<br/>false';
}

Answer 2

There is no generic solution to handle this because no predefined set of characters that meets your needs exists.
However, you can add the range of accented characters.
[ ,-\.0-9A-Za-z\{\}À-ž]
Also, see How to allow utf-8 charset in preg_match? for information on matching against a specific character set.