// Match utf-8 words (remove the \p{N} if you don't want to index words with numbers)
preg_match_all("/\p{L}[\p{L}\p{N}\p{Mn}\p{Pd}'\x{2019}]*/u", $text, $t1);

Index: isearch.inc.t
===================================================================
RCS file: /forum21/install/forum_data/src/isearch.inc.t,v
retrieving revision 1.71
diff -u -r1.71 isearch.inc.t
--- isearch.inc.t       29 Apr 2009 20:34:12 -0000      1.71
+++ isearch.inc.t       2 May 2009 09:19:07 -0000
@@ -17,7 +17,7 @@
        // Match utf-8 words (remove the \p{N} if you don't want to index wordswith numbers)
        preg_match_all("/\p{L}[\p{L}\p{N}\p{Mn}\p{Pd}'\x{2019}]*/u", $text, $t1);
        foreach ($t1[0] as $v) {
-               if (isset($v[51]) || !isset($v[2])) continue;   // word too long or too short
+               // if (isset($v[51]) || !isset($v[2])) continue;   // word too long or too short
                $a[] = _esc($v);
        }