Replace a word between an html tag

Question

I am trying to get texts between two symbols or HTML tags, then find and replace all the words 'sun' with 'moon' within that HTML tag or < with <. for example I have a $text like below:

<body>
    <p>
    text text sun text text...
       <tag> some text here sun some text here </tag>
    text text sun text sun text...
       <span>
           <tag> text here sun text text sun text </tag>
           <tag> sun text here sun text sun, sun </tag>
       </span>
    </p>
</body>

I would like to find all the sun's between the <tag>...</tag> tags and replace them with moon so that the result will be:

<body>
    <p>
    text text sun text text...
       <tag> some text here moon some text here </tag>
    text text sun text sun text...
       <span>
           <tag> text here moon text text moon text </tag>
           <tag> moon text here moon text moon, moon </tag>
       </span>
    </p>
</body>

I tried $text = str_replace("sun","moon",$text); but this will replace all the matches in or out of the tags. Also tried preg_replace("/(<tag>)(.*?)sun(.*?)(<\/tag>)/", "$2 moon $3", $text); it doesn't work as expected.

You should look into PHP's [DomDocument](http://php.net/manual/en/class.domdocument.php) for parsing HTML. Don't use regular expressions, since it's not suited for unregular content like HTML. https://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags — M. Eriksson, Sep 01 '18 at 09:48
[Try with `preg_replace_callback`](https://www.phprun.org/M8vpHR). But better to use a HTML parser. — bobble bubble, Sep 01 '18 at 09:50

score 2 · Answer 1 · answered Sep 01 '18 at 09:45

If the text inside the tags doesn't contain any <s, one option is to search for sun, followed by lookahead for non-< characters, followed by <\/tag>:

$str = "<body>
    <p>
    text text sun text text...
       <tag> some text here sun some text here </tag>
    text text sun text sun text...
       <span>
           <tag> text here sun text text sun text </tag>
           <tag> sun text here sun text sun, sun </tag>
       </span>
    </p>
</body>";
$result = preg_replace("/sun(?=[^<]*<\/tag>)/", "moon", $str);

Output:

<body>
    <p>
    text text sun text text...
       <tag> some text here moon some text here </tag>
    text text sun text sun text...
       <span>
           <tag> text here moon text text moon text </tag>
           <tag> moon text here moon text moon, moon </tag>
       </span>
    </p>
</body>

That said, using regular expressions to parse HTML is not recommended except in the most trivial cases - consider using a proper HTML parser instead, if at all possible.

Thank you. But I also want to replace `<` between that tag with `<`! — mac, Sep 01 '18 at 09:54
This is the first time that's been mentioned - if that's a requirement, please include it in your question itself, thanks — CertainPerformance, Sep 01 '18 at 09:56
I didn't know `<` should be mentioned. Question edited. thanks. — mac, Sep 01 '18 at 10:15

score 1 · Accepted Answer · answered Sep 01 '18 at 10:18

This should probably be done by use of a HTML parser as mentioned in comments. If you want to uses regex, I'd use preg_replace_callback (use of anonymous function >= PHP 5.3).

$text = preg_replace_callback('~<tag>\K.*?(?=</tag>)~s', function ($m) {
  return preg_replace(['~\bsun\b~i','~<~','~>~'], ["moon","&lt;","&rt;"], $m[0]);
}, $text);

See PHP demo at PhpRun.org - without anonymous function:

function rep_tag ($m) {
  return preg_replace(['~\bsun\b~i','~<~','~>~'], ["moon","&lt;","&rt;"], $m[0]);
}

$text = preg_replace_callback('~<tag>\K.*?(?=</tag>)~s', 'rep_tag', $text);

Regex demo and explanation at regex101

score 0 · Answer 3 · answered Sep 01 '18 at 10:00

0

Search: (<tag>)(.*?)sun(.*?)(<\/tag>)

Replace by: \1moon\4

answered Sep 01 '18 at 10:00

Replace a word between an html tag

3 Answers3