JQuery / PHP / Wordpress Professional needed

Job ID: 35833666

Budget: $30 – $250 USD

It's about updating PHP and JQuery.

We have a wordpress site that has an outdated JQUERY library. Currently we are keeping it running with the plugin "jQuery Migrate Helper".
We want to change that. Unfortunately, we can't work on the live page as postings happen here. So we cloned this to a dev server so we don't affect the original server.
There we should take out the old jquery, update the development so we can update the furthermore the PHP version of the server. PHP is currently at 7.2 and we should upgrade it to >7.4 or if possible 8.x.

Especially problematic is a booking form that can be used to book seats/tables and food on certain dates. For this there is also a backend which lets you edit these. JQuery is also used here.
In addition, opening hours are set in the backend and displayed in the form of a traffic light (open and closed) and a speech bubble on the main page.
Changes are probably necessary here as well.

Actually it is kept alive by the jquery helper....
Also, the page is misaddressed... meaning we have multiple hardcoded addresses like https or https://www. .....
Changing the backend URL to https does not give the correct result, but multiple certificate errors.
So we are forced to use ssl-insecure-fixer-plugin on live site... this should not happen, if the code is well transformed, changing url and changing htaccess and wp-config should be ok.

Finally there is a bug (maybe caused by this outdated library) in the tool. This sometimes causes tables to be marked as busy even though they are not. This bug also needs to be fixed.

I would also explain once the whole mechanics of booking and opening hours and accordingly would have to be checked at the end if everything works as we need it to.

So we need someone who is really fit in the technical part of wordpress. Especially with absolute focus on programming and not so much on design, etc.
It's really a programming project. So please only apply if you are really fit in PHP 7.x and 8.x and JQUERY cross-version, as well as the possibilities of Wordpress.
Related categories: PHP JavaScript AJAX WordPress jQuery / Prototype