For example I have a string with markup (from html node):

hello, this is dog

"h<em>e<strong>llo, thi</strong>s i</em><strong>s d</strong>og"

What is the most correct way to find some words in it (let's say "hello" and "dog"), wrap them in a span (make a highlight) and save all the markup?

Desired output is something like this (notice properly closed tags)

<span class="highlight">h<em>e<strong>llo</strong></em></span><strong>,</strong> <em><strong>thi</strong>s<em> i</em><strong>s <span class="highlight"><strong>d</strong>og</span>

Looks the same as it should:

hello, this is dog