Regular Expression Recursion

How can I setup a regular expression to replace nested text with replacement text. I can't explain it very well, but say I want to replace [asdf] with <asdf>, and my sample text is:

Code:

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[asdf]adsfasdf[asdf]adsfadsf[/adsf][/adsf]

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I end up with this:

Code:

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<asdf>adsfasdf[asdf]adsfadsf</adsf>[/adsf]

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Or something similiar depending on the modifiers I use.

How can I accomplish replaces like this?

well cant you use str_replace()?

edit:

wrong function... fixed it

I can, but not straight out of the box. I'd only want to replace [asdf] if it has a matched [/asdf]. I can ensure this easily with a regular expression.

replace() isn't a function (yes, yes, I'm crude. I know you probably meant str_replace()), and no, if you bothered to look at the sample he provided.. that wouldn't even work in the first place.

now, I'm not very good with regular expressions, and I really would have to know a lot more about your situation and what you're trying to do before I could even begin to try to provide you with a more detailed expression. However, for all relevant purposes, this would work and convert the strings you used to what you were looking for. It's not very flexible, though. I would probably wait for CornedBee, because he's crazy with regular expressions.

PHP Code:

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<?php
  $text = '[tag]test text here[tag]test2 text2 here2[/tag]test2[/tag]';
  //i want to return:
  //       <tag>test text here[tag]test2 text2 here2</tag>test2[/tag]

  echo $text . "\n\n";

  echo preg_replace('/\[(.*)\](.*)\[(.*)\](.*)\[\/(.*)\](.*)\[\/(.*)\]/i', "<$1>$2[$3]$4</$5>$6[/$7]", $text);
?>

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this returned:

Code:

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[tag]test text here[tag]test2 text2 here2[/tag]test2[/tag]

<tag>test text here[tag]test2 text2 here2</tag>test2[/tag]

---

Feel free to elaborate a little more on the type of flexibility you're looking for (and if there is going to be multiple nested tags or not?). In my sample, you NEED to have a nested tag for it to return anything useful. If the nested tags are optional in your case, it would be useless.

Oh, and mine's also sloppy because I made a 'catch-all,' as I wasn't sure what kind of characters your tags could contain.

edit: if you want, this is a great resource for learning about regular expressions.

oh i see. try this, it might help. Just a quick google search:

http://haacked.com/archive/2004/10/2...matchhtml.aspx

Sorry, I don't think I explained myself very well. What I am trying to do is replace any occurrence of [list][/list]with <ul></ul>. So if I have 40 instances of these [list] tags, I want to replace all 40 of them. That's all well and good, except for when they're nested (which in HTML would create sub lists), ie:

Code:

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[list]adsf[list]asdf[/list][/list]

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Which should be replaced with:

Code:

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<ul>asdf<ul>asdf</ul></ul>

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(Note, this isn't correct HTML-wise, I am handling <li> as well, but that's irrelevant for this example, as those cannot be nested).

can there be lists within the nested lists? eg, to produce:

Code:

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<ul>
  <li>
    <ul>
      <li>
        <ul>
          <li>hello!</li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

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or can there just be two levels of lists?

I'm guessing I somehow have to use (?R), recursive patterns: php.net/manual/en/reference.pcre.pattern.syntax.php but for the life of me, I can't figure out how.

Quote:

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Originally Posted by kows

can there be lists within the nested lists? eg, to produce:

Code:

---

<ul>
  <li>
    <ul>
      <li>
        <ul>
          <li>hello!</li>
        </ul>
      </li>
    </ul>
  </li>
</ul>

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or can there just be two levels of lists?

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Any level of nesting (although, I know using recursive regular expressions there is a defined limit controlled by the ini).