How do I define a libpcre regexp for arabic characters?

Question

I need to define a PCRE regexp for certain spam-ish words in Arabic/Persian alphabet to be used in drupal spam module. The problem is that the usual PCRE regexp is apparently unable to find patters in Arabic alphabets.

For example, while /bad word/ flags instances of 'bad word', but

/کلمه بد/i

Is unable to flag 'کلمه بد'.

Answer 1

I have no problem with that if I use the u (Unicode) PCRE modifier:

$string = 'کلمه بد';

if (preg_match('~\p{Arabic}~u', $string) > 0)
{
    var_dump('contains Arabic characters');

    if (preg_match('~کلمه بد~ui', $string) > 0)
    {
        var_dump('contains spam-ish Arabic characters');
    }
}

string(26) "contains Arabic characters"
string(35) "contains spam-ish Arabic characters"

It runs just fine on IDEOne.com too. Be sure to save your files (and convert input data) in (to) UTF-8.