$re = '/(?<=\]: ).*(?=\[[^[\]]*:[^[\]]*\])/m';
$str = '00:0qwe8.0 donald controller duck [02009&123@##]: Some more sring here Model number 420 Family [Super-cool] [15b31013^^@#][15b:31013][test]';
preg_match_all($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