Problem with 'substr' PHP function on non english characters

Hello!
‘substr‘ php function get error character in end of non english character string.

I offer to use this function insted:

function _substr($str, $length, $minword = 3)
{
    $sub = '';
    $len = 0;

    foreach (explode(' ', $str) as $word)
    {
        $part = (($sub != '') ? ' ' : '') . $word;
        $sub .= $part;
        $len += strlen($part);

        if (strlen($word) > $minword && strlen($sub) >= $length)
        {
            break;
        }
    }
    return strtolower($sub . (($len < strlen($str)) ? '...' : ''));
}

Thanks!

https://ww.wp.xz.cn/plugins/contus-video-gallery/