php regex转义特殊字符[重复]

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Is there a PHP function that can escape regex patterns before they are applied? 1 answer
是否有一个PHP函数可以在应用regex模式之前转义它们?1回答

I wrote the following code (yes it does work) and was wondering why I don't need to escape the '<' and '>' characters inside the pattern since they are considered 'special' characters by the php manual.

我编写了以下代码(是的，它确实可以工作)，我想知道为什么不需要在模式中转义“<”和“>”字符，因为php手册认为它们是“特殊”字符。

http://www.php.net/manual/en/function.preg-quote.php

var_dump(preg_match('/<[A-Za-z][A-Za-z0-9]*>/', "<html>", $matches));

echo "<pre>";
var_dump(htmlentities($matches[0]));
echo "</pre>";

output:

输出:

int(1) 
string(12) "<html>"

2 个解决方案

#1

Only the characters listed on this page need to be escaped in PHP regex matching/replacing.

只需要在PHP regex匹配/替换中转义此页面中列出的字符。

While < and > can act as delimiter, it doesn't need to be escaped in the given example because you already have /(slash) acting as a delimiter.

虽然 <和> 可以作为分隔符，但是在给定的示例中不需要转义，因为已经有/(斜杠)作为分隔符。

Referring to the link in question

指的是相关的链接

The preg_quote() function may be used to escape a string for injection into a pattern and its optional second parameter may be used to specify the delimiter to be escaped.

preg_quote()函数可用于将字符串转义到模式中，其可选的第二个参数可用于指定要转义的分隔符。

#2

< and > aren't meta characters is most contexts.

<和> 不是元字符是大多数上下文。

However they are used as such for:

然而，它们被用于:

named capture groups (?P<name>)
名叫捕捉组(? P <名称> )
lookbehind assertions (?<=...)
向后插入断言(? < =…)

So that's why preg_quote plays it safe and escapes them. It's arguably redundant, since escaping ( and ? would be sufficient. But it doesn't hurt either.

这就是为什么preg_quote将其置于安全的位置，并避开它们。它可以说是多余的，因为转义(和?就足够了。但它也不疼。

#1