$re = '/^(?![\d.]{18})\d{1,3}(?:\.\d{3})*(?:,\d\d?)?$/m';
$str = '1.000.000.000.000
1.000.000.000.000,00
1
1,00
123,45
10.000.000.000.000
10.000.000.000.000,00
10.000.000.000.000.000
10.000.000.000.000.000,00';
preg_match_all($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