$re = '/^(?!0+(?:[,.]0+)?$)\d+(?:[,.][05])?$/m';
$str = '0,5
0.5
0.7
0,9
1,0
1.0
1.4
1,4
1.5
0
0,0
0000.000
00000,00000';
preg_match_all($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