PHP has a special pattern \w to define alphabetic characters. But it doesn’t find words on other languages but English.
Use the following regular expression to find words on different languages in a string in Unicode (UTF):
$text = "your text here";
$res = preg_match_all('/[a-z\x80-\xFF]+/uim', $text, $matches);
if ($res) print_r($matches);
Using the modificator ‘u’ is necessary to search in Unicode.