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Home Backend Development PHP Tutorial javascript - 正则替换replace中$1的用法

javascript - 正则替换replace中$1的用法

Jun 06, 2016 pm 08:21 PM
javascript php

<code>preg_replace("/([&?]uid=)[^?&]*/",'$1173','http://localhost/mobile/index.php?c=wish&uid=181')

//输出:http://localhost/mobile/index.php?c=wish73
</code>
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如上面$replacement ($1173)表示的,php以为我要把$11加上73,但其实我是想让 $1加上173,请问怎样改才能符合我的预期?

刚刚在写问题的时候突然想到把$replacement改成$01说不定可以,没想到真可以了,现在是这样'$01173'

另外,同样的$replacement($1173)放到js里表现的结果却是我预期的,那js里想要$11加上73怎么办?

回复内容:

<code>preg_replace("/([&?]uid=)[^?&]*/",'$1173','http://localhost/mobile/index.php?c=wish&uid=181')

//输出:http://localhost/mobile/index.php?c=wish73
</code>
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Copy after login

如上面$replacement ($1173)表示的,php以为我要把$11加上73,但其实我是想让 $1加上173,请问怎样改才能符合我的预期?

刚刚在写问题的时候突然想到把$replacement改成$01说不定可以,没想到真可以了,现在是这样'$01173'

另外,同样的$replacement($1173)放到js里表现的结果却是我预期的,那js里想要$11加上73怎么办?

试试$01173

JS只是比较智能一点,它发现你的正则里面没有11个分组,所以会把$1173拆分为$1173两个部分。但是当分组数量达到11个以上时它也就会以能够匹配到的最大的分组来替换了,比如:

'abcdefffgg'.replace(/(f+)fgg/, '$1173'); // abcdeff173,(替换的是第1个分组,ff)
'abcdefffgg'.replace(
    /(f+)(a?)(a?)(a?)(a?)(a?)(a?)(a?)(a?)(a?)(fgg)/,
    '$1173'); // abcdefgg73(替换的是第11个分组,fgg)
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要想在上面的第二个例子里替换第一个分组,可以用$01173,由于分组最大只能到99,而01已经满了2位数,所以JS不会再去尝试检查第三位数。你可以在PHP里试试这种方法,我没测试,不知道可不可行。

至于你说的,想让JS在不足11个分组的时候匹配$11应该是做不到的。

在replace第二个参数里面$实际上是告诉正则表达式引擎,接下来的是一个反向引用(有的语言或工具里面也用\标识),是对正则表达式中匹配出来的组的引用,在你的例子里面就是 ([&?]uid=)所匹配出来的内容。

我对PHP不是很熟。
回答你的javascript的问题,在js里面$1代表的第一个被匹配到的group。所以结果是正确。

如果你想要$11这个字符串的加上73的话,用这个就可以了$$1173

详细说明可参照这里:http://deerchao.net/tutorials/regex/regex.htm#backreference

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