- Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.25, 8.4.1 - 8.4.12
- subdomain
<?php
preg_match('/^[^.]*\.(?=\w+\.\w+$)/','subdomain.example.com',$matches);
$subdomain = isset($matches[0]) ? trim($matches[0],'.') : '';
echo $subdomain;