PCRE正则表达式重叠匹配 [英] PCRE regular expression overlapping matches

问题描述

我有以下字符串

001110000100001100001

和该表达式

/[1]....[1]/g

这将进行两次匹配

但是我希望它也可以使两者之间的模式相匹配，也就是说，重叠的1

but i want it to also match the pattern between those both with lookbehind so to say, the overlapping 1

我完全不知道，这怎么工作?而不是0，它可以是任何字符

i have absolutely no clue, how can this work ? instead of 0 it can be any characters

推荐答案

一个常见的技巧是在未锚定的积极前瞻中使用捕获技术.将此正则表达式与preg_match_all一起使用:

A common trick is to use capturing technique inside an unanchored positive lookahead. Use this regex with preg_match_all:

(?=(1....1))

请参见 regex演示

值在$matches[1] 中:

$re = "/(?=(1....1))/"; 
$str = "001110000100001100001"; 
preg_match_all($re, $str, $matches);
print_r($matches[1]);

请参见提前引用:

环顾四周实际上是匹配字符，但随后放弃匹配，仅返回结果:匹配或不匹配.这就是为什么它们被称为断言"的原因.它们不使用字符串中的字符，而仅声明是否可以进行匹配.

Lookaround actually matches characters, but then gives up the match, returning only the result: match or no match. That is why they are called "assertions". They do not consume characters in the string, but only assert whether a match is possible or not.

如果要在正则表达式中存储正则表达式的匹配项，则必须在正则表达式内将正则表达式周围的括号括起来，如下所示:(?=(regex)) .

If you want to store the match of the regex inside a lookahead, you have to put capturing parentheses around the regex inside the lookahead, like this: (?=(regex)).

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