$re = '/(?<!\d)(?<!\d\.)(?:\d{1,3}(?:,\d{3})*|\d+)(?:\.\d{1,2})?(?!\.?\d)/m';
$str = '120,000.00
40,000
456,667
334532
123,223,333.34';
preg_match_all($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