使用先前的反向引用作为命名捕获组的名称 [英] Use previous backreference as name of named capture group

问题描述

有没有办法使用对前一个捕获组的反向引用作为命名捕获组的名称?这可能是不可能的，如果不是，那么这是一个有效的答案.

Is there a way to use a backreference to a previous capture group as the name of a named capture group? This may not be possible, if not, then that is a valid answer.

以下内容:

$data = 'description: some description';
preg_match("/([^:]+): (.*)/", $data, $matches);
print_r($matches);

产量:

(
    [0] => description: some description
    [1] => description
    [2] => some description
)

我尝试使用对第一个捕获组的反向引用作为命名捕获组 (?<$1>.*) 告诉我这是不可能的，或者我只是没有正确做:

My attempt using a backreference to the first capture group as a named capture group (?<$1>.*) tells me it's either not possible or I'm just not doing it correctly:

preg_match("/([^:]+): (?<$1>.*)/", $data, $matches);

产量:

警告:preg_match(): 编译失败:(?< at offset 12

Warning: preg_match(): Compilation failed: unrecognized character after (?< at offset 12

想要的结果是:

(
    [0] => description: some description
    [1] => description
    [description] => some description
)

这使用 preg_match 进行了简化.使用 preg_match_all 时，我通常使用:

This is simplified using preg_match. When using preg_match_all I normally use:

$matches = array_combine($matches[1], $matches[2]);

但我想我可能比那更狡猾.

But thought I might be slicker than that.

推荐答案

总之，这是不可能的，你可以坚持你目前一直在使用的编程方式.

In short, it is not possible, you can stick to the programming means you have been using so far.

组名称(应该由最多 32 个字母数字组成字符和下划线，但必须以非数字开头)在编译时解析，并且反向引用值仅在运行时已知.请注意，这也是您不能在后视中使用反向引用的原因(尽管您清楚地看到 /(x)y[az](?<!\1)/ 是可以的，PCRE 正则表达式引擎另有看法，因为它无法通过反向引用推断后视的长度).

Group names (that should consist of up to 32 alphanumeric characters and underscores, but must start with a non-digit) are parsed at compile time, and a backreference value is only known at run-time. Note it is also a reason why you cannot use a backreference inside a lookbehind (altghough you clearly see that /(x)y[a-z](?<!\1)/ is OK, the PCRE regex engine sees otherwise as it cannot infer the length of the lookbehind with a backreference).

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