$re = '/Server Version: \K\d+(?:\.\d+)+(?= Kubernetes)/m';
$str = 'Client Version: openshift-clients-4.3.0-201910250623-88-g6a937dfe Server Version: 4.3.0 Kubernetes Version: v1.16.2:q';
preg_match_all($re, $str, $matches, PREG_SET_ORDER, 0);
// Print the entire match result
var_dump($matches);
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php