如何修复“致命错误：未捕获错误：调用未定义函数 get_header()”

Question

I am trying to put this website back online. The error message is the following:

Fatal error: Uncaught Error: Call to undefined function get_header() in /homepages/25/d584099293/htdocs/clickandbuilds/X3DSYSTEMS/wp-content/themes/x3dprotheme/index.php:4 Stack trace: #0 {main} thrown in /homepages/25/d584099293/htdocs/clickandbuilds/X3DSYSTEMS/wp-content/themes/x3dprotheme/index.php on line 4

The client told me he "accidentally reset the domain".

First when I went on the website, I had an error message about Wordfence and I did what I needed to do to correct it (here what I did:

After moving a site or deleting some files, I see: PHP Fatal error: Unknown: Failed opening required /var/www/html/wordfence-waf.php

I removed the firewall setup manually.

Then I got this new error message about index.php :

In this index.php, here is what I found:

<?php get_header(); ?>

<?php get_footer(); ?>

I try to get this website back online.

The webhost is 1and1 IONOS. I can't log into WP, but I have SFTP access.

Answer 1

What webhost is this? Maybe if we know, we can ascertain what the "domain reset" involved and backtrack the fix once we know exactly what those steps entailed.

When these sorts of things happen to me (I manage about 30 WordPress sites), the first thing I do is disable all plugins, and sometimes if I can't actually log into WordPress, I remove the plugins via SFTP or through cPanel .

You're stuck though if you have no access to the host. It'll extremely difficult to solve this without access to the server or control panel for the hosting environment. Do you at least have SFTP access?

Answer 2

This looks like a path to a core theme file.

If you are using child theme, you should be able to update the parent via the theme settings found in your dashboard, without data loss from style sheets, etc. you made in your child theme.

This would work like the backup restore as suggested above, but without the need to get into cPanel or FTP.

Answer 3

The client changed the "target" with his webhost, and the site is back online.

There was also a problem with revolution slider, but anyway, the problem looks solved.