// Created on savesnippets.com · https://savesnippets.com/d99GIzYH1ad2dC
<?php
function wordCountU(string $text): int {
    preg_match_all('/[\p{L}\p{N}]+/u', $text, $matches);
    return count($matches[0]);
}

echo wordCountU("Hello world");                // 2
echo wordCountU("café au lait, s'il vous plaît"); // 6
echo wordCountU("日本語のテスト 123");           // 3 (depending on tokenizer)