Form_validation regex_match

[eluser]Exangelus[/eluser]
I already worked that out and I'm currently using this code:

Code:

if(stripos($rule, '[') !== false && substr($rule, -1) == ']')

However, simple regexp do seem to work while more complex one's do not. I'm still figuring out with which exact characters (or combinations) it goes wrong..

Cheers!