使用PHP剥离HTML注释，但离开条件 [英] Stripping HTML Comments With PHP But Leaving Conditionals

问题描述

我目前使用PHP和一个正则表达式来从一个页面中去掉所有的HTML注释。脚本运行良好...有点太好了。它删除所有评论，包括我的条件评论。这是我得到的：

 <？php 
函数回调（$ buffer）
 { 
 return preg_replace（'/<！ - （。| \s）*？ - > /'，''，$ buffer）; 
} 
 
 ob_start（callback）; 
？> 
 ... HTML源代码在这里... 
<？php ob_end_flush（）; ？> 
  

由于我的正则表达式不太热，我在尝试找出如何修改模式以排除条件注释，例如：

 <！ -  [if！IE]><！ - ; 
< link rel =stylesheethref =/ css / screen.csstype =text / cssmedia =screen/> 
<！ - <！[endif]  - > 
 
<！ -  [if IE 7]> 
< link rel =stylesheethref =/ css / ie7.csstype =text / cssmedia =screen/> 
<！[endif]  - > 
 
<！ -  [if IE 6]> 
< link rel =stylesheethref =/ css / ie6.csstype =text / cssmedia =screen/> 
<！[endif]  - > 
  

干杯

解决方案

由于注释不能嵌套在HTML中，正则表达式可以在理论上完成这项工作。仍然，使用某种解析器将是更好的选择，特别是如果你的输入不能保证形成良好。

这里是我的尝试。要只匹配正常的注释，这将工作。它已经变成一个怪物，对不起。我已经测试了它相当广泛，它似乎做得很好，但我不给保修。

 <！ - （?! \s *（?: \ [if [^ \]] +] |<！|>）） *  - > 
  

说明：

 <！ - ＃01：<！ - 
（？！＃02：look-ahead： b \ * *＃03：任意数量的空格
（？：＃04：非捕获组，任何：
 \ [if [^ \]] +]＃05： [if ...]
 |< ;!＃06：或< ;!
 |>＃07：或>
）＃08：捕获组
）＃09：结束先行
（？：＃10：非捕获组：
（?!->）＃11： - >
。＃12：吃下面的char，它是评论的一部分
）*＃13：结束非捕获组，重复
  - > ＃14： - > 
  

步骤＃02和＃11至关重要。 ＃02确保以下字符不表示条件注释。之后，＃11确保以下字符不表示注释的结束，而＃12和＃13则引起实际匹配。

使用全局和dotall标志。

要做相反的事情（只匹配条件注释），它会是这样：

 <！（ - ）？（？= \ [ \\] \1>）。）*<！\ [endif\] \1> 
  

说明：

 < ;! ＃01：< ;! 
（ - ）？ ＃02：两个破折号，可选
（？= \ [）＃03：一个位置后跟[
（？：＃04：非捕获组：
 ＃05：不后跟
的位置<！\ [endif\] \1>＃06：<！[endif]>或<！ ;（取决于＃02）
）＃07：end of look-ahead 
。＃08：吃下面的char，它是注释的一部分
）*＃09：end非捕获组，重复
 <！\ [endif\] \1> ＃10：<！[endif]>或<！[endif]  - > （取决于＃02）
  

同样，使用global p>

步骤＃02是因为downlevel-revealed语法，参见：MSDN - 关于条件注释。

允许或期望空格。在适当的情况下，将 \s * 添加到表达式中。

I'm currently using PHP and a regular expression to strip out all HTML comments from a page. The script works well... a little too well. It strips out all comments including my conditional comments in the . Here's what I've got:

<?php
  function callback($buffer)
  {
        return preg_replace('/<!--(.|\s)*?-->/', '', $buffer);
  }

  ob_start("callback");
?>
... HTML source goes here ...
<?php ob_end_flush(); ?>

Since my regex isn't too hot I'm having trouble trying to figure out how to modify the pattern to exclude Conditional comments such as:

<!--[if !IE]><!-->
<link rel="stylesheet" href="/css/screen.css" type="text/css" media="screen" />
<!-- <![endif]-->

<!--[if IE 7]>
<link rel="stylesheet" href="/css/ie7.css" type="text/css" media="screen" />
<![endif]-->

<!--[if IE 6]>
<link rel="stylesheet" href="/css/ie6.css" type="text/css" media="screen" />
<![endif]-->

Cheers

解决方案

Since comments cannot be nested in HTML, a regex can do the job, in theory. Still, using some kind of parser would be the better choice, especially if your input is not guaranteed to be well-formed.

Here is my attempt at it. To match only normal comments, this would work. It has become quite a monster, sorry for that. I have tested it quite extensively, it seems to do it well, but I give no warranty.

<!--(?!\s*(?:\[if [^\]]+]|<!|>))(?:(?!-->).)*-->

Explanation:

<!--                #01: "<!--"
(?!                 #02: look-ahead: a position not followed by:
  \s*               #03:   any number of space
  (?:               #04:   non-capturing group, any of:
    \[if [^\]]+]    #05:     "[if ...]"
    |<!             #06:     or "<!"
    |>              #07:     or ">"
  )                 #08:   end non-capturing group
)                   #09: end look-ahead
(?:                 #10: non-capturing group:
  (?!-->)           #11:   a position not followed by "-->"
  .                 #12:   eat the following char, it's part of the comment
)*                  #13: end non-capturing group, repeat
-->                 #14: "-->"

Steps #02 and #11 are crucial. #02 makes sure that the following characters do not indicate a conditional comment. After that, #11 makes sure that the following characters do not indicate the end of the comment, while #12 and #13 cause the actual matching.

Apply with "global" and "dotall" flags.

To do the opposite (match only conditional comments), it would be something like this:

<!(--)?(?=\[)(?:(?!<!\[endif\]\1>).)*<!\[endif\]\1>

Explanation:

<!                  #01: "<!"
(--)?               #02: two dashes, optional
(?=\[)              #03: a position followed by "["
(?:                 #04: non-capturing group:
  (?!               #05:   a position not followed by
    <!\[endif\]\1>  #06:     "<![endif]>" or "<![endif]-->" (depends on #02)
  )                 #07:   end of look-ahead
  .                 #08:   eat the following char, it's part of the comment
)*                  #09: end of non-capturing group, repeat
<!\[endif\]\1>      #10: "<![endif]>" or "<![endif]-->" (depends on #02)

Again, apply with "global" and "dotall" flags.

Step #02 is because of the "downlevel-revealed" syntax, see: "MSDN - About Conditional Comments".

I'm not entirely sure where spaces are allowed or expected. Add \s* to the expression where appropriate.

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