Why doesn't the regular expression find the second match?

Question

PHP

$str = '1.9.2017'; // или 10.9.2017 или 1.10.2017
$str = preg_replace('/(^|\.)(\d\.)/', '${1}0$2', $str);
var_dump($str); // 01.9.2017, а ожидалось, что будет 01.09.2017

What am I doing wrong? Thanks in advance!

Answer 1

$str = preg_replace('/(?<=^|\.)(\d\.)/', '0$1', $str);

Answer 2

Good afternoon.
Try like this