PHP: Regex replace word using wildcard characters in Lookbehind Assertions

Question

I'm looking to create a PHP Regex script that can match and replace words within a string.

The regex needs to match only complete words, which I can easily accomplish with:

/\b(SEARCH_TERM)\b/

The problem I am having is that some of the strings contain html elements as such as <a> tags and <img> tags, where the href and src attributes may sometimes contain the to-be-replaced word within their path. If this word is replaced within these elements, then the link or image will no longer work.

Example, replace the word 'test' with 'SEARCH_TERM' for the following example string:

my test string <a href="http://www.google.com?q=my+test+string">link</a>

Would return:

my SEARCH_TERM string <a href="http://www.google.com?q=my+SEARCH_TERM+string">link</a>

Whereas I need it to ignore the href attribute text and return:

my SEARCH_TERM string <a href="http://www.google.com?q=my+test+string">link</a>

I've looked at using Regex's Lookbehind Assertions (As just below), but variable length wildcard characters are not allowed.

/(?<!(href|src)=.*)\b(SEARCH_TERM)\b/

Note: I specifically need to do this with Regex, and not a DOM parser.

Use [HTML parser](http://stackoverflow.com/questions/3577641/parsing-and-processing-html-xml)..don't use regex..Believe me,its more simple to parse html using a parser than doing it with regex — Anirudha, Jul 03 '13 at 05:19
As mentioned at the bottom, I specifically need to do this with Regex. — ticallian, Jul 03 '13 at 05:24
Why is that you people always *need* to not use the better solution (which is just as supported as the less optimal solution)? What kind of limitation is preventing from using a decent DOM parser? — Madara's Ghost, Jul 03 '13 at 05:33

score 2 · Accepted Answer · edited May 23 '17 at 11:56

2

As I mentioned you need to use an html parser.

But if you want it

/\btest\b(?=[^>]*(<|$))/s

Above regex would match only if there's < or end of string(not line) ahead somewhere without matching >

NOTE

This would not work if your text itself contains >.

For example

 hello>world

Hence the reason you should use a parser

edited May 23 '17 at 11:56

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answered Jul 03 '13 at 05:28

Anirudha

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`REPLACE other text.` – Madara's Ghost Jul 03 '13 at 05:36
@MadaraUchiha that would be another good technique if the size of html is small – Anirudha Jul 03 '13 at 05:38
It isn't a technique. It's an easy demonstration on where your regex breaks. If you have an html tag, nothing behind it gets replaced. – Madara's Ghost Jul 03 '13 at 05:40
@MadaraUchiha have you tried..it replaces even if there are no tags.I have used `$` if you have observed it properly. – Anirudha Jul 03 '13 at 05:41
@MadaraUchiha ok..there's 1 case in which it could break..see the note – Anirudha Jul 03 '13 at 05:45

PHP: Regex replace word using wildcard characters in Lookbehind Assertions

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