$re = '/^(0(,\d{0,2})?|-?[1-9]\d*(,\d{1,2})?|-0,(0[1-9]|[1-9]\d?))$/m';
$str = 'Deverá aceitar:
0
0,
0,0
0,00
0,010
0,00000000000000000000002
0,01
0,99
0,1
1234567890,99
-1234567890,99
-0,01
-0,99
1,00
-1,00
-1,012
Não poderá aceitar:
-0
-0,
-0,00
-,01 a -,99
//Sequencia vazio
01,00
01
0012';
preg_match_all($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