Replace only inside tag brackets

Question

I want the regex to use in preg_replace() to replace text only inside a tag (between "<" and ">"), without affect the text out of angle brackets limit. Like this example:

$html = '<div class="REPLACE_ME" id="my_id">this REPLACE_ME cannot be replaced</div>';
$html = preg_replace('/\bREPLACE_ME\b/', 'REPLACED', $html);

then, the result expected in $html variable must be like this:

<div class="REPLACED" id="my_id">this REPLACE_ME cannot be replaced</div>

The regex cannot be around the quotes, because I have other variants like:

<REPLACE_ME>this REPLACE_ME cannot be replaced</REPLACE_ME>
<div REPLACE_ME="my_attribute">this REPLACE_ME cannot be replaced</div>

Already answered here: http://stackoverflow.com/a/1732454/597122 — rockerest, Aug 05 '14 at 17:59
possible duplicate of [RegEx match open tags except XHTML self-contained tags](http://stackoverflow.com/questions/1732348/regex-match-open-tags-except-xhtml-self-contained-tags) — rockerest, Aug 05 '14 at 18:00
Thank for your tip @rocketest, but this reference don't help-me, because I don't want to find only matches tags. — rcsalvador, Aug 05 '14 at 18:25
Hey Rodrigo, it was a tongue-in-cheek posting, but the underlying point is this: it doesn't SPECIFICALLY answer your question, but the overall answer is ---> Do NOT parse HTML with REGEX. You simply cannot do it without creating black holes. It's a bad idea. — rockerest, Aug 05 '14 at 18:30

Avinash Raj · Accepted Answer · 2014-08-05T18:17:19.247

Regex:

<[^>]*\KREPLACE_ME(?=[^>]*?>)

Replacement string:

REPLACED

DEMO

PHP code would be,

<?php
$mystring = <<<'EOT'
<div class="REPLACE_ME" id="my_id">this REPLACE_ME cannot be replaced</div>
<REPLACE_ME>this REPLACE_ME cannot be replaced</REPLACE_ME>
<div REPLACE_ME="my_attribute">this REPLACE_ME cannot be replaced</div>
EOT;
echo preg_replace('~<[^>]*\KREPLACE_ME(?=[^>]*?>)~', 'REPLACED', $mystring);
?>

Output:

<div class="REPLACED" id="my_id">this REPLACE_ME cannot be replaced</div>
<REPLACED>this REPLACE_ME cannot be replaced</REPLACED>
<div REPLACED="my_attribute">this REPLACE_ME cannot be replaced</div>

Explanation:

< Matches the lesser than < symbol.
[^>]* Matches any character not of > zero or more times.
\K Discards the previously matched characters. So from < upto the REPLACE_ME string would be discarded.
REPLACE_ME Matches the string REPLACE_ME.
(?=[^>]*?>) Lookahead asserts that the following characters must be anything not of > symbol followed by >. This ensures that the matched string REPLACE_ME is within <> block.

score -2 · Answer 2 · answered Aug 05 '14 at 17:59

-2

Perhaps something like this

I think what you're looking for is a positive lookahead or lookbehind.

So the regex I used is:

(?<=<).*?(REPLACE_ME).*?(?=>)

The (?<=<) means make sure there is a < to the left and
then (?=>) means make sure there is a > to the right

Also, consider using an XML parser. Regex is very limited when it comes to tags like this.

answered Aug 05 '14 at 17:59

skamazin

757
5
12

[Take a look here](http://regex101.com/r/tJ1yD2/3) I'm fairly certain it matches only the `REPLACE_ME`s that are within a tag. Please give me an example where the regex fails. – skamazin Aug 06 '14 at 11:39

Replace only inside tag brackets

2 Answers2