$re = '/^\[?(?:(?:\[(?:(?:[0-9]{1,}\,?){1,})\])\,?){1,}\]?$/mi';
$str = '[[1,2,3],[4,5,6],[7,8,9]]
[1,2,3],[4,5,6],[7,8,9]
[1,25,3],[4,52,6],[7,8,9]
[[1,2,3]]
[[1],[2]]';
preg_match_all($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