Strange result of the regular season, how to treat?

Question

PHP

Greetings!

From the string you need to get all the words that are more than 3 characters long. I wrote a regular expression and displayed the result, and there questions, instead of some characters, and parts of words begin and end in strange places.

- Checked regular here https://regex101.com/r/MGYN0I/2
- File encoding utf-8.
- Checked the script on Windows and Linux.

What to do?

$string = "организация охраны 21 617";
preg_match_all("/[а-я]{4,}/i", $string, $keywords);
print_r($keywords);

Array
(
    [0] => Array
        (
            [0] => ганиза�
            [1] => ия
            [2] => ан�
        )

)

Answer 1

Add modifier u:

preg_match_all("/[а-я]{4,}/ui", $string, $keywords);