$re = '/eventtype=\K\S+/';
$str = '(STUNNEL-SECURITY AND NOT (
eventtype=sec-stunnel-client-*
OR eventtype=sec-stunnel-crl-*
OR eventtype=sec-stunnel-loaded-*
OR eventtype=sec-stunnel-loading-*
OR eventtype=sec-stunnel-no-*
OR eventtype=sec-stunnel-openssl-*
OR eventtype=sec-stunnel-sconnect-*
OR eventtype=sec-stunnel-server-*
OR eventtype=sec-stunnel-service-*
OR eventtype=sec-stunnel-session-*
OR eventtype=sec-stunnel-socket-*
OR eventtype=sec-stunnel-ssl-*
OR eventtype=sec-stunnel-stats-*
OR eventtype=sec-stunnel-threading-*
OR eventtype=sec-stunnel-timeout-*
OR eventtype=sec-stunnel-various-*
) )';
preg_match_all($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