$re = '/(?:[^\r\n,{}]+)(?:,(?=[^}]*{)|\s*{[\s]*})/';
$str = '#colorful {
color: #0000;
}
.my > .empty + .selector {
}
[this] {}
* > div {
background-image: url(http://...);
}
* .one {
}';
preg_match_all($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