$re = '/\[(quote)=[^]]+\](?>(?R)|.)*?\[\/quote]/si';
$str = 'one,two,3,(4,five),six,(seven),,(8,9,ten),eleven,(twelve,13,14,fifteen)
[quote=test][quote=test]for sure[/quote]
Test
[/quote]
[this should not be removed]
Dont remove me
[quote=test]
s
[quote=test]for s
[quote=test]for sure[/quote]
sure[/quote]
Test2
[/quote]
x
';
preg_match_all($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