$re = '/\bobject-group\b\S*(?:\s+(?!object-group\b)\S*)*/';
$str = 'object-group network FTP
description FTP Access
network-object host BCD1
network-object host BCD2
object-group network NTP
description NTP Access
network-object host ABC1
network-object host ABC2
network-object host ABC3
object-group service sample_service tcp
description Ports 1 2 3
port-object range 80 81
port-object eq pop3
port-object eq imap4
port-object range 443 444
object-group service 8080 tcp
description Servers';
preg_match_all($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