如何在正则表达式中添加限制

Question

我有一个 Regex 函数，可以让我替换文本中出现 X 的单词。我尝试添加条件，如果单词在标签 <h1>,<h2>,<h3> 和图像 alt 信标中，则不要替换。请有人帮我编辑函数以添加此条件。

public function str_ireplace_n($search, $replace, $subject, $occurrence)
{
    $search = preg_quote($search);
    return preg_replace("/^((?:(?:.*?$search){" . --$occurrence . "}.*?))$search/i", "$replace", $subject);
}

示例：

$text = "Lorem ipsum dolor sit amet, consectetur adipiscing elit. <h1>Lorem ipsum dolor sit</h1> Proin libero erat, malesuada eget volutpat vitae, efficitur vitae ipsum. Vivamus et <h2>Lorem ipsum dolor sit</h2> justo non quam laoreet euismod. Ut eget dapibus ligula. <img src="url" alt="Lorem ipsum dolor sit"/> Vestibulum vestibulum."

// I replace the second Lorem in this text by a link
$text = $this->str_ireplace_n('Lorem', ' <a href="' . $domain . '" alt="">Lorem</a> ', $text, 2); //2 for the second occurence

//The result will add a link on the Lorem inside the <h1> and I want to avoid this.
//I want the Regex do nothing in the case where the keyword is in h1 h2 or alt of image

我没有选择要替换的"Lorem"，随机出现。当发生在 <h1>/<h2> 或图像 alt.

上时，我必须确保我不做任何事情

提前致谢

Answer 1

就我个人而言，我会先使用 preg_split 之类的东西：

$string = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. <h1>Lorem ipsum dolor sit</h1> Proin libero erat, malesuada eget volutpat vitae, efficitur vitae ipsum. Vivamus et <h2>Lorem ipsum dolor sit</h2> justo non quam laoreet euismod. Ut eget dapibus ligula. <img src="url" alt="Lorem ipsum dolor sit"/> Vestibulum vestibulum.';

$split = preg_split('/(<[^\/]+(?:\/|<\/[^>]+)>)/', $string, null, PREG_SPLIT_DELIM_CAPTURE);

这给了你这个（这是我们需要做的基本事情）：

Array
(
    [0] => Lorem ipsum dolor sit amet, consectetur adipiscing elit. 
    [1] => <h1>Lorem ipsum dolor sit</h1>
    [2] =>  Proin libero erat, malesuada eget volutpat vitae, efficitur vitae ipsum. Vivamus et 
    [3] => <h2>Lorem ipsum dolor sit</h2>
    [4] =>  justo non quam laoreet euismod. Ut eget dapibus ligula. 
    [5] => <img src="url" alt="Lorem ipsum dolor sit"/>
    [6] =>  Vestibulum vestibulum.
)

现在我们已将这些项目隔离在标签内。所以现在我们可以遍历这个集合并检查前导字符是或不是 < 并了解它是在标签内部还是外部。只要您的标签以 </...> 或 />.

结尾，这就应该有效

基本上 HTML 标签 + 内容成为分隔符，我们也捕获它。

重点是简单的正则表达式无法解析 HTML，因为它不是常规语言。所以我们必须在 PHP 中做一些工作来将它们联系在一起。我们可以分解它并使用简单的正则表达式简化问题，就像我在这里所做的那样。

$subject = 'Lorem ipsum dolor sit amet, consectetur adipiscing elit. <h1>Lorem ipsum dolor sit</h1> Proin libero erat, malesuada eget volutpat vitae, efficitur vitae ipsum. Vivamus et <h2>Lorem ipsum dolor sit</h2> Lorem justo non quam laoreet euismod. Ut eget dapibus ligula. <img src="url" alt="Lorem ipsum dolor sit"/> Vestibulum vestibulum.';

//word to replace
$search = 'Lorem';
//stuff to replace with
$replace = '<a href="Lorem">foo</a>';
 //what match to replace
$occurrence = 2;

function str_ireplace_n($search, $replace, $subject, $occurrence){
    $search = preg_quote($search);

    //separate the HTML from the "body" text
    $split = preg_split('/(<(?:h1|h2|h3|img)[^\/]+(?:\/|<\/[^>]+)>)/', $subject, null, PREG_SPLIT_DELIM_CAPTURE);
    //the number of current matches
    $match = 0;

    foreach($split as &$s){
        //if strpos < is 0 it's the first character - meaning its part of HTML (we don't want that)
        //if it matches search 
        if(0 !== strpos($s,'<') && preg_match('/\b'.$search.'\b/i', $s)){
            //increment the match counter
            ++$match;
             //replace the match if it's the nth one
            if($match == $occurrence)  $s = preg_replace('/\b'.$search.'\b/i',$replace,$s);
        }
    }

    return implode($split);
}

echo str_ireplace_n($search, $replace, $subject, $occurrence);

输出：

Lorem ipsum dolor sit amet, consectetur adipiscing elit. <h1>Lorem ipsum dolor sit</h1> 
 Proin libero erat, malesuada eget volutpat vitae, efficitur vitae ipsum. Vivamus et 
  <h2>Lorem ipsum dolor sit</h2> <a href="Lorem">foo</a> justo non quam laoreet euismod. 
  Ut eget dapibus ligula. <img src="url" alt="Lorem ipsum dolor sit"/> Vestibulum vestibulum.

这是被替换的部分<a href="Lorem">foo</a>

我添加了几行 returns 以提高可读性（在输出中），又添加了另一行 "Lorem" （在输入中），因为 HTML 标签之外没有第二行匹配上。在任何情况下，如果您注意到，HTML 标签中的任何内容都没有被修改。在这种情况下，只有第二场比赛发生了变化。

并不是 100% 清楚您需要什么（这些类型的问题通常都是这种情况），所以我尝试解释如何做，而不是仅仅做。

Sandbox

如何在正则表达式中添加限制

How to add restriction in regex

php

regex

preg-replace