通过正则表达式替换匹配中的单个字符 [英] Replace a single character within a match via Regex

问题描述

我有一个简单的模式，我正在尝试对其进行查找和替换.当它们被数字包围时，它需要用句点替换所有破折号.

I have a simple pattern that I am trying to do a find and replace on. It needs to replace all dashes with periods when they are surrounded by numbers.

替换这些中的句点:

3-54
32-11
111-4523mhz

像这样:

3.54
32.11
111.4523mhz

但是，我不想替换以下内容中的破折号:

However, I do not want to replace the dash inside anything like these:

Example-One
A-Test

我尝试使用以下方法:

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

然而，这将替换整个匹配而不是中间.你如何只替换匹配的一部分?

However, this will replace the entire match instead of just the middle. How do you only replace a portion of the match?

推荐答案

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.

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