Solved: symbol validation check question

Personally I would match characters I want instead of those I don't want. Right now you can use chines letters in your folder name, are you allowed to do so?

PHP Code:

$re = '/\W/'; // \W matches any non-word character (equal to [^a-zA-Z0-9_])

$str = $this->input->post('folder');

$is_correct_foldername = !preg_match($re, $str) ? true : false; 


This will give you false on every character except:
a-z
A-Z
0-9
_

And spaces?

There's only one rule - please don't tell anyone to go and read the manual.  Sometimes the manual just SUCKS!