Wordpress Reverse Proxy Plugin

reverse-proxy.php

<?php
/**
 * @package Reverse Proxy
 */
/*
Plugin Name: Reverse Proxy
Plugin URI: https://instrumentalapp.com/
Description: Reverse proxy setup for Instrumental blog
Version: 1.0
Author: James Paden
Author URI: https://instrumentalapp.com
*/


// Change to match the desired subfolder, no leading or tralling slash
define("RP_SUBFOLDER", "blog");

function rp_is_login_page() {
    return in_array($GLOBALS['pagenow'], array('wp-login.php', 'wp-register.php'));
}

if ( $_SERVER["REMOTE_ADDR"] != "127.0.0.1" && !is_admin() && !rp_is_login_page() && $_GET["preview"] != "true" ) {
    add_action( 'init', function () {
    	if (!$_SERVER["HTTP_X_IS_REVERSE_PROXY"]) {
    		//not coming from us, 404 it.
    		header($_SERVER["SERVER_PROTOCOL"]." 404 Not Found");
    		exit;
    	}
    });

    //From http://stackoverflow.com/questions/772510/wordpress-filter-to-modify-final-html-output
    ob_start();
    add_action('shutdown', function() {
        $final = '';
        $levels = count(ob_get_level());
        for ( $i = 0; $i < $levels; $i++ ) {
            $final .= ob_get_clean();
        }

        // Apply any filters to the final output
        $final = str_replace("http://" . $_SERVER["HTTP_HOST"], "https://" . $_SERVER["HTTP_X_ORIGINAL_HOST"] . "/" . RP_SUBFOLDER, $final);
        echo $final;
    }, 0);
}

//This would only be needed if you are using Yoast SEO 
add_filter( 'wpseo_canonical', 'lc_persistent_canonical' );

/**
 * Make this a universal change since we want this applied everywhere
 * even if we aren't viewing view Reverse Proxy.
 *
 * Replace the "final_url" with the correct Final URL for the site
 *
 * @param      $canonical string
 */
function lc_persistent_canonical( $canonical ) {
	$canonical = str_replace( site_url(), RP_FINAL_URL . RP_SUBFOLDER . '/', $canonical );
	return $canonical;
}

z-httpd-vhosts.conf

# Example code for Apache config
# Put this inside the <VirtualHost> directive
<Location /blog>
    RequestHeader set X-Is-Reverse=Proxy true
    RequestHeader set X-Original-Host yourwebsite.com
    ProxyPass http://yourpressableblog.com
    ProxyPassReverse http://yourpressableblog.com
</Location>

z-nginx-config.txt

# Example code for Nginx config
# Put this inside the "server {" section
location /blog/ {
  proxy_set_header X-Original-Host $host;
  proxy_set_header X-Is-Reverse-Proxy "true";
  proxy_pass_header Set-Cookie;
  proxy_cookie_path / /blog/;
  proxy_pass http://yourpressableblog.com/;
}