- Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
- СССР
<?php
$string = "Союз Советских Социалистических Республик";
$expr = '/(?<=\s|^)\w/iu';
preg_match_all($expr, $string, $matches);
$result = implode('', $matches[0]);
echo $result = strtoupper($result);