警告:preg_replace():未知修饰符']' [英] Warning: preg_replace(): Unknown modifier ']'

问题描述

我遇到以下错误:

警告:preg_replace():第38行上xxx.php中的未知修饰符']'

Warning: preg_replace(): Unknown modifier ']' in xxx.php on line 38

这是第38行的代码:

<?php echo str_replace("</ul></div>", "", preg_replace("<div[^>]*><ul[^>]*>", "", wp_nav_menu(array('theme_location' => 'nav', 'echo' => false)) )); ?>

如何解决此问题?

推荐答案

为什么会发生错误

在PHP中，正则表达式需要包含在一对 delimiters <中/a>.分隔符可以是任何非字母数字，非反斜杠，非空格字符； /，#，~是最常用的.请注意，也可以使用括号样式的定界符，其中左括号和右括号是开始和结束定界符，即<pattern_goes_here>，[pattern_goes_here]等都有效.

Why the error occurs

In PHP, a regular expression needs to be enclosed within a pair of delimiters. A delimiter can be any non-alphanumeric, non-backslash, non-whitespace character; /, #, ~ are the most commonly used ones. Note that it is also possible to use bracket style delimiters where the opening and closing brackets are the starting and ending delimiter, i.e. <pattern_goes_here>, [pattern_goes_here] etc. are all valid.

在以下两种情况下通常会出现"未知修饰符X "错误:

The "Unknown modifier X" error usually occurs in the following two cases:

当您的正则表达式缺少分隔符时.

当您在内部使用定界符 而没有转义时.

在这种情况下，正则表达式为<div[^>]*><ul[^>]*>. regex引擎将从<到>的所有内容都视为regex模式，然后将所有内容视为修饰符.

In this case, the regular expression is <div[^>]*><ul[^>]*>. The regex engine considers everything from < to > as the regex pattern, and everything afterwards as modifiers.

Regex: <div[^>  ]*><ul[^>]*>
       │     │  │          │
       └──┬──┘  └────┬─────┘
       pattern    modifiers

]是未知的修饰符，因为它出现在结束的>分隔符之后.这就是PHP抛出该错误的原因.

] here is an unknown modifier, because it appears after the closing > delimiter. Which is why PHP throws that error.

根据模式的不同，未知修饰词的抱怨也可能是关于*，+，p，/或)或几乎任何其他字母/符号的.只有imsxeADSUXJu是有效的PCRE修饰符.

Depending on the pattern, the unknown modifier complaint might as well have been about *, +, p, / or ) or almost any other letter/symbol. Only imsxeADSUXJu are valid PCRE modifiers.

修复很容易.只需使用任何有效的定界符包装您的正则表达式模式即可.在这种情况下，您可以选择 〜 并获得以下信息:

The fix is easy. Just wrap your regex pattern with any valid delimiters. In this case, you could chose ~ and get the following:

~<div[^>]*><ul[^>]*>~
│                   │
│                   └─ ending delimiter
└───────────────────── starting delimiter

如果尽管使用了定界符但仍收到此错误，则可能是因为模式本身包含了所述定界符的未转义出现.

If you're receiving this error despite having used a delimiter, it might be because the pattern itself contains unescaped occurrences of the said delimiter.

/foo[^/]+bar/i当然会引发错误.因此，如果它出现在正则表达式中的任何位置，则可以使用 \ 反斜杠对其进行转义:

/foo[^/]+bar/i would certainly throw an error. So you can escape it using a \ backslash if it appears anywhere within the regex:

/foo[^\/]+bar/i
│      │     │
└──────┼─────┴─ actual delimiters
       └─────── escaped slash(/) character

如果您的正则表达式模式包含很多次的定界符，这将是一项繁琐的工作.

This is a tedious job if your regex pattern contains so many occurrences of the delimiter character.

当然，更简洁的方法是完全使用其他定界符.理想情况下，一个字符不会出现在正则表达式模式中的任何位置，例如#-#foo[^/]+bar#i.

The cleaner way, of course, would be to use a different delimiter altogether. Ideally a character that does not appear anywhere inside the regex pattern, say # - #foo[^/]+bar#i.

• PHP regex分隔符
• http://www.regular-expressions.info/php.html
• 如何在PHP中将ereg表达式转换为preg?(缺少分隔符)
• …中的未知修饰符"/"?是什么?(使用 preg_quote() )

• PHP regex delimiters
• http://www.regular-expressions.info/php.html
• How can I convert ereg expressions to preg in PHP? (missing delimiters)
• Unknown modifier '/' in …? what is it? (on using preg_quote())

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