$re = '/^\[GROUP2]([\s\S]+)(?=\n\n|\z)/m';
$str = '[GROUP1]
;This is something I don\'t want
COMMAND(value:test)
COMMAND(value:[type="submit"])
COMMAND(value:test)
COMMAND(value:test)
[GROUP2]
;This is something I don\'t want
COMMAND(value:test)
COMMAND(value:[type="submit"])
COMMAND(value:test)
COMMAND(value:test)
';
preg_match_all($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