PHP-如何用正则表达式按条件替换字符串

Question

我有一个字符串：

{include "abc"}

{literal} 

function xyz() {

       "ok";

   }

{/literal}

{abc}

{123 }

我只想替换{literal}标签中的所有{到{{和}到}} 。 结果将是：

{{include "abc"}}

{{literal}}

   function xyz() {

       "ok";

   }

   //... something contain { and }

{{/literal}}

{{abc}}

{123 }}

有人可以帮助我，谢谢

Answer 1

您可以使用以下模式进行操作：

$pattern = '~(?:(?<={literal})[^{]*(?:{(?!/literal})[^{]*)*+|[^{}]*)([{}])\K~'

$text = preg_replace($pattern, '$1', $text);

演示

图案细节：

~                       # pattern delimiter
(?:                     # non-capturing group
    (?<={literal})      # lookbehind: preceded by "{literal}"
                        # a lookbehind doesn't capture any thing, it is only a test
    [^{]*               # all that is not a {
    (?:
        {(?!/literal})  #/# a { not followed by "/literal}"
        [^{]*
    )*+                 # repeat as needed
  |                     # OR
    [^{}]*              # all that is not a curly bracket,
                        # (to quickly reach the next curly bracket)
)
([{}])                  # capture a { or a } in group 1
\K                      # discards all on the left from match result
                        # (so the whole match is empty and nothing is replaced,
                        # the content of the capture group is only added 
                        # with the replacement string '$1')
~

注意：此模式假定{literal}不能嵌套且始终关闭。 如果{literal}可以保持未关闭状态，则可以强制执行以下默认行为： “未关闭的{literal}被视为处于打开状态，直到字符串结尾” 。

为此，您可以将捕获组更改为([{}]|(*COMMIT)(*F)) 。 当第一个分支[{}]失败时，这意味着到达字符串的结尾。 (*COMMIT)动词在模式失败后强制正则表达式引擎停止字符串中的所有研究，而(*F)强制其失败。 因此{literal}之后的所有内容保持不变。

Answer 2

正则表达式：

(?s)(?<=\{literal\}).*?(?=\{\/literal\})(*SKIP)(*F)|([{}])

替换字符串：

\1\1

演示