Code igniter is restrictive over permitted url characters (a good thing!), and it’s simple enough to edit the permitted_uri_config option to add more charaters. However, what if you’re dealing with Japanese charaters in the url?
Well (after a little searching) it turns out that this isn’t too difficult to fix as the config value is a regex and one can add the kanji charater ranges in a similar fashion to the standard ascii ‘a-z’ syntax:
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_-';
$config['permitted_uri_chars'] = '一-龠ぁ-んァ-ヴーａ-ｚＡ-Ｚ０-９a-z 0-9~%.:_-';