Replace “content-area” of themes 404 page with plugin?

Question

So I don't want to dive into the whys behind what I need to do but I have a very important piece of code that I need to insert into the 404 page regardless of the theme as a replacement of the content-area div. So below the get_header in replacement of the content-area and before the get_sidebar/get_footer.

Currently I have to install this piece of code into every themes 404 page before I can install it on my multisite, I'd like to accomplish this through a plugin but can't seem to override the themes 404 page.

Answer 1

According to the Template Page hierarchy, https://developer.wordpress.org/files/2014/10/wp-hierarchy.png the only template page WP will load is 404.php

But, you might try this in your mu-plugins:

//Some function to check database to see if this URL should exist if ( ! checkIfPageExists( $_SERVER['REQUEST_URI'] ) ) { //Set 404 Status status_header( "404" ); get_header(); //do your custom 404 code here get_footer(); }

I'm not sure it'll work, but give it a try