Regex DO NOT match text inside tag

Question

I am trying to create a link tag <a href="{url}" title="{keyword}">keyword</a> onto a given text when it find that keyword. But that keyword should NOT already inside an <a></a> tag already and it should also not match href and title attribute. I'm using PHP

For example:

*NOTE. My usecase text don't have space

Text = thisiscatfish

Keyword = catfish

Expected Output = thisis<a href="#" title="catfish">catfish</a>

BUT if

Text = iam<a href="www.catfish.com" title="catfish">catfish</a>

Keyword = fish

Expected Output: iam<a href="www.catfish.com" title="catfish">catfish</a>

*NOTE it should NOT match href and title attribute and replace it.

What I have tried https://paiza.io/projects/WYvDVTUMDg0kFOUo6NEHpQ

Problem

My solution so far it matching and replacing href and title as well. How can I modify my regex to not match href and title attribute as well?

function replaceText($text, $keyword, $url) {
    
    $pattern = "/(?!>)$keyword(?!<\/a>)/i";
    
    $replaceWith = "<a href='$url' title='$keyword'>$keyword</a>";
    
    $newText = preg_replace($pattern, $replaceWith, $text);
    
    return $newText;
}

$text = '<p>thisiscatfish</p>';

$newText = replaceText($text, 'catfish', 'www.catfish.com');

$newText2 = replaceText($newText, 'fish', 'www.fish.com');
echo $newText2;

You can do this by use of [`(*SKIP)(*F)`](https://stackoverflow.com/questions/24534782/how-do-skip-or-f-work-on-regex) and further I'd recommend to use `preg_quote` for escaping the input. Change to `$pattern = "/<]*>(*SKIP)(*F)|".preg_quote($keyword,"/")."/i";`. Probably wiser to use some html parser for such kind of tasks, not sure : ) — bobble bubble, Sep 19 '21 at 03:57
@bobblebubble Thanks alot, your pattern does exclude matching the title and href attribute but still match the text inside So it have nested link now. So I added original regex to become `$pattern = "/<]*>(*SKIP)(*F)|(?!>)".preg_quote($keyword,"/")."(?!<\/a>)/i"` And it seems working great. Any suggestion? Otherwise please post as answer and I'll accept — cjmling, Sep 19 '21 at 04:54

score 0 · Answer 1 · answered Sep 20 '21 at 16:38

What you are attempting to do, should not be attempted. RegEx cannot parse HTML. Regular Expressions are for regular languages, HTML is an Irregular language. Therefore it simply cannot handle what you are asking for.

To further emphasize this point, let me point you in the direction of one of the most powerful answers to garnish this forum.

Regex DO NOT match text inside tag

BUT if

What I have tried https://paiza.io/projects/WYvDVTUMDg0kFOUo6NEHpQ

Problem

1 Answers1