$re = '/^[+-]?\d+\.\d{1,12}$/m';
$str = '1.1
0
1.123456789123
a1223
0000.1111
1.abv
0.00
1.0
0.0
';
preg_match_all($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