如果没有用大括号括起来，则正则表达式匹配关键字

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问题描述

在 PHP 变量中，我有一些包含一些关键字的文本.这些关键字目前大写.我希望它们保持大写并用大括号括起来，但只有一次.我正在尝试编写升级代码，但每次运行时它都会将关键字包装在另一组大括号中.

In a PHP variable I have some text that contains some keywords. These keywords are currently capitalised. I would like them to remain capitalised and be wrapped in curly brackets but once only. I am trying to write upgrade code but each time it runs it wraps the keywords in another set of curly brackets.

我需要使用什么 REGEX 来单独匹配关键字而不匹配它(如果它是 {KEYWORD}).

What REGEX do I need to use to match the keyword alone without also matching it if it is {KEYWORD}.

例如文本变量为:

$string = "BLOGNAME has posted COUNT new item(s),

TABLE

POSTTIME AUTHORNAME

You received this e-mail because you asked to be notified when new updates are posted.
Best regards,
MYNAME
EMAIL";

我的升级代码是:

$keywords = array('BLOGNAME', 'BLOGLINK', 'TITLE', 'POST', 'POSTTIME', 'TABLE', 'TABLELINKS', 'PERMALINK', 'TINYLINK', 'DATE', 'TIME', 'MYNAME', 'EMAIL', 'AUTHORNAME', 'LINK', 'CATS', 'TAGS', 'COUNT', 'ACTION');
foreach ($keywords as $keyword) {
    $regex = '|(^\{){0,1}(\b' . $keyword . '\b)(^\}){0,1}|';
    $replace = '{' . $keyword . '}';
    $string = preg_replace($regex, $replace, $string);
}

我的 REGEX 目前根本无法正常工作，它正在剥离一些空格，并且在每次运行时在大多数(但不是全部)关键字周围放置更多大括号.我究竟做错了什么?有人可以纠正我的正则表达式吗?

My REGEX is currently not working well at all, it is stripping some spaces and also on each run placing more curly brackets around most (but not all) keywords. What am I doing wrong? Can someone correct my regex?

推荐答案

您正在寻找 否定断言.它们不像在字符类中那样使用 ^ 语法编写，而是使用 (?<!...) 和 (?!...)代码>.在你的情况下:

You are looking for negative assertions. They are not written using the ^ syntax as in character classes but as (?<!...) and (?!...). In your case:

'|(?<!\{)(\b' . $keyword . '\b)(?!\})|';

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