如何匹配正则表达式中的多个（N）空格？

Question

我有一个正则表达式(?<={% start %}).*?(?={% end %})，可以匹配两个自定义标记之间的所有内容。

问题是如果标签内有空格（例如“{％start％}”）并且我添加\s+?条件，则正则表达式失败。以下代码不起作用：(?<={%\s+?start\s+?%}).*?(?={%\s+?end\s+?%})我在PHP中收到错误：

preg_match_all(): Compilation failed: lookbehind assertion is not fixed length at offset 25

如果我删除lookahead / lookbehind：({%\s+?(start|end)\s+%})，则相同的正则表达式有效。

请告知。

Answer 1

描述

试试这个permlink

[{]%\s*?\b([^}]*start[^}]*)\b\s*?%[}]\s*?\b(.*?)\b\s*?[{]%\s*\b([^}]*end[^}]*)\b\s*%[}]

这将匹配{%和%}括号内的所有文字，并会在将值放入群组之前自动修剪文字。

组0获取整个匹配字符串

1. 获取开始标记文字
2. 获取内部文字
3. 获取结束标记文字



声明

如果您将复杂数据嵌套到sub中，这可能会有一些边缘情况，其中正则表达式将失败，如果是这样，那么使用正则表达式可能不是此任务的最佳工具。

摘要

[{]%\s*?\b([^}]*start[^}]*)\b\s*?%[}]\s*?\b(.*?)\b\s*?[{]%\s*\b([^}]*end[^}]*)\b\s*%[}]
Char class [{] matches one of the following chars: {
% Literal `%`
\s 0 to infinite times [lazy] Whitespace [\t \r\n\f] 
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
1st Capturing group ([^}]*start[^}]*) 
Negated char class [^}] infinite to 0 times matches any char except: }
start Literal `start`
Negated char class [^}] infinite to 0 times matches any char except: }
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
\s 0 to infinite times [lazy] Whitespace [\t \r\n\f] 
% Literal `%`
Char class [}] matches one of the following chars: }
\s 0 to infinite times [lazy] Whitespace [\t \r\n\f] 
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
2nd Capturing group (.*?) 
. 0 to infinite times [lazy] Any character (except newline) 
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
\s 0 to infinite times [lazy] Whitespace [\t \r\n\f] 
Char class [{] matches one of the following chars: {
% Literal `%`
\s infinite to 0 times Whitespace [\t \r\n\f] 
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
3rd Capturing group ([^}]*end[^}]*) 
Negated char class [^}] infinite to 0 times matches any char except: }
end Literal `end`
Negated char class [^}] infinite to 0 times matches any char except: }
\b Word boundary: match in between (^\w|\w$|\W\w|\w\W)
\s infinite to 0 times Whitespace [\t \r\n\f] 
% Literal `%`
Char class [}] matches one of the following chars: }

PHP示例

带示例文字 {% start %} this is a sample text 1 {% end %}{% start %} this is a sample text 2 {% end %}

<?php
$sourcestring="your source string";
preg_match_all('/[{]%\s*?\b([^}]*start[^}]*)\b\s*?%[}]\s*?\b(.*?)\b\s*?[{]%\s*\b([^}]*end[^}]*)\b\s*%[}]/i',$sourcestring,$matches);
echo "<pre>".print_r($matches,true);
?>

$matches Array:
(
    [0] => Array
        (
            [0] => {% start %} this is a sample text 1 {% end %}
            [1] => {% start %} this is a sample text 2 {% end %}
        )

    [1] => Array
        (
            [0] => start
            [1] => start
        )

    [2] => Array
        (
            [0] => this is a sample text 1
            [1] => this is a sample text 2
        )

    [3] => Array
        (
            [0] => end
            [1] => end
        )

)