preg_replace('/([0-9])-([0-9])/', '$1.$2', $string);

应该可以解决问题:)

更多解释:

通过在正则表达式中使用 ( 和 )，您可以创建一个组.该组可用于替换.$1 被第一个匹配的组替换，$2 被第二个匹配的组替换，依此类推.

By using ( and ) in a regular expression, you create a group. That group can be used in the replacement. $1 get replaced with the first matched group, $2 gets replaced with the second matched group and so on.

这意味着，如果您(仅作为示例)将 '$1.$2' 更改为 '$2.$1'，该操作将交换两个数字.在您的情况下，这不是有用的行为，但也许它可以帮助您更好地理解原理.

That means that if you would (just for example) change '$1.$2' to '$2.$1', the operation would swap the two numbers. That isn't useful behavior in your case, but perhaps it helps you understand the principle better.