使用RegExp在HTML标记内获取内容 [英] Get content inside HTML tags with RegExp

问题描述

我想使用regexp从大型表单元文件中提取内容，并使用PHP处理数据.

I'd like to extract the content from a large file of table cells using regexp and process the data using PHP.

这是我要匹配的数据:

<td>Current Value: </td><td>100.178</td>

我尝试使用此正则表达式来匹配并检索文本:

I tried using this regexp to match and retrieve the text:

preg_match("<td>Current Value: </td><td>(.+?)</td>", $data, $output);

但是，我收到未知修饰符"警告，并且变量$ output变空.

However I get an "Unknown modifier" warning and my variable $output comes out empty.

我该怎么做-您能否简要介绍该解决方案的工作原理，以便我能理解为什么我的代码不起作用?

How can I accomplish this - and could you give me a brief summary of how the solution works so I can try to understand why my code didn't?

推荐答案

您需要在正则表达式周围添加定界符:

You need to add delimiters around your regex:

preg_match("#<td>Current Value: </td><td>(.+?)</td>#", $data, $output);

标准定界符是/，但是如果您愿意，也可以使用其他非字母数字字符(这在这里很有意义，因为正则表达式本身包含斜杠).就您而言，正则表达式引擎认为您想使用尖括号作为定界符-失败了.

The standard delimiter is /, but you can use other non-alphanumeric characters if you wish (which makes sense here because the regex itself contains slashes). In your case, the regex engine thought you wanted to use angle brackets as delimiters - and failed.

另一个提示(除了不应该使用regexen解析HTML"的规范性训诫(在这样的特定情况下，我认为这是完全可以的)):使用([^<>]+)而不是(.*?).这样可以确保您的正则表达式永远不会跨越嵌套标记，这是处理标记语言时常见的错误来源.

One more tip (aside from the canonical exhortation "Thou shalt not parse HTML with regexen" (which I think is perfectly OK in a specific case like this)): Use ([^<>]+) instead of (.*?). This ensures that your regex will never travel across nested tags, a common source of errors when dealing with markup languages.

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