$re = '/^[1-9][0-9]?[0-9]?$|^1000$/m';
$str = '0.0
0
1.2
0.1
0.23
.2345
2.3
1
111
2
5
9
10
15
50
1000
';
preg_match_all($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