I do apprecciate this may sound like the usual question, but it is not. Just to let you understand I do not need to install one of the many SEO Plugin and change it on the box before content is published.
My scenario is the following:
I have a page which Querystring may change the content shown on page and I'd like to do the same with meta description and title if that would the the case.
In a normal template file I would probably look for the querystring and stick an if condition. Problem is that template is not mine and when it will be updated my changes will be lost. So I thought to a slightly more complicate solution.
Using the Wordpress php_exec plugin I will embed the php lines in the content section delegating to them the task, but using normal Wordpress core functions. This is a must, because I can't use a simple if condition in the content area, not without having two meta descriptions or title in the page, with the latter added in the wrong place.
So what I need to do is understanding how Wordpress is adding both the meta in the final HTML. Is this something related to the add_action('wp_head', ... something here)?
As additional info, I am not using Yoast SEO plugin, so I can't rely on any of his additional function.
Thanks for your help Andrea