PHP preg_replace_callback，只替换 1 个反向引用? [英] PHP preg_replace_callback, replace only 1 backreference?

问题描述

使用preg_replace_callback，是否可以只替换一个反向引用?还是我必须退回整个东西?

Using preg_replace_callback, is it possible to replace only one backreference? Or do I have to return the entire thing?

我只是想用引号将令牌的默认值包装起来.

I'm just trying to wrap the token's default value with quotes.

$str = 'This is a {$token|token was empty}';
$str = preg_replace_callback('~{\$\w+\|(.*)?}~i', function($match) {
    //$match[1] is "token was empty"
    //I want to just replace $match[1], but it needs me to return the whole thing
}, $str);

我是否必须获取更多的反向引用，以便我能够构建一个新版本的令牌并返回它，我不能只替换反向引用 1?谢谢.

Do I have to grab more backreferences so I'm able to build out a new version of the token and return that, I can't just replace backreference 1? Thanks.

推荐答案

我是否必须获取更多的反向引用才能构建新版本的令牌并返回，我不能只替换反向引用 1?

Do I have to grab more backreferences so I'm able to build out a new version of the token and return that, I can't just replace backreference 1?

您有两个选择:

1. 如您所说，使用额外的反向引用来构造替换字符串，或者
2. 使用环视仅匹配您要替换的部分.

通常我建议使用第一种方法，因为第二种方法效率较低，并且在某些情况下可能导致无效匹配(当前瞻和后向可能重叠时).在这种情况下，就没有问题了.

Usually I recommend using the first approach as the second is a bit less efficient and can lead to invalid matches in some cases (when the lookahead and behind can overlap). In this case there would be no problem tho.

第二个选项的示例是:

preg_replace_callback('~{\$\w+\|\K(?:[^{}]+)?(?=})~i', function($match){
    // $match[0] contains what used to be the first capturing group.
    // return the value you want to replace it with
    // (you can still use the capturing group if you want, but it's unnecessary)
});

• \K 是一种从实际匹配中排除它之前的所有内容的方法(就像我们在那里有一个可变长度的lookbehind).
• (?=}) 是一个前瞻，表示以下必须是 } 但不包括它自己的匹配.
• \K is a way to exclude everything before it from the actual match (like if we had a variable length lookbehind there).
• (?=}) is a lookahead, saying that the following has to be a } but does not include it in the match it self.

这篇关于PHP preg_replace_callback，只替换 1 个反向引用?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！