How to find unclosed html tags or make the weird styling as a result contained in one element?

I have a tinyMCE editor that allows HTML.

Sometimes a user pastes a table from a website or some other content that is not copied in its entirety, resulting in broken html.

I display this content on a page which breaks sometimes due to this. Example image:

What is the best way to fix this? Is there a way to isolate this html somehow so the content of this element does not affect the rest of the page? Or is there a function to automatically close all tags?

I just simply display the content like this:

<div class="editwindow">
    <h4 class="mt-0 m-b-30 header-title bigheader">'.$gettopcatcontent['title'].'</h4>
    <div class="content_tekst">'.$gettopcatcontent['content'].'</div>
    '.$versiondate.'
</div>

Answer

You can possibly use DOMDocument::loadHTML. It will produce warnings for malformed HTML.

Set libxml_use_internal_errors to true and then use libxml_get_errors to handle the warnings.