If you have updated wordpress to the latest version and your wordpress website is not working after updating php then there is an issue with plugins that you have installed on your wordpress website or it can be a theme conflict that doesn’t work with php 8 update due to php code compatibility issues.
If wordpress website not working after updating php 8 and wordpress to latest version then you need to downgrade wordpress to previous version and make website up and starting debugging issue with latest version in local system or create a staging website and update in staging and then update live website.
As soon as you update wordpress to the latest version and update php 8 then it breaks your website then you need to download a copy of your website to your local machine and update php 8 and wordpress and check for any possible errors and fix if php8 deprecated functions and rewrite php code on your website.
What is the Problem With PHP 8.0 with WordPress?
Php 8 on wordpress will not be compatible with plugins and themes on your wordpress website and as soon as you update your wordpress website will break and to avoid this issue you need to update php 8 in local system using xampp, wamp or if you have mac then lamp and then update php 8 and write php 8 compatible code.
The main issue is plugins and themes will not be written with php latest version compatibility or wordpress compatibility and plugin authors or theme authors need to update the code as per latest php 8 recommendations and write compatible code.
How to Fix WordPress not working with php 8 update
Follow below methods to fix wordpress not compatible or not working with php 8 version.
Code Compatibility
If wordpress websites break after updating php 8 then the php code written in plugins or theme files are not compatible with the newer version of php8 and you need to write code which is compatible with the new version of php 8 and update php 8.
Downgrade to previous PHP version
Due to incompatibility issues with php 8 ike plugins and themes will not work with latest version of php and to make your website live after updating wordpress, you need to downgrade php version to previous version like php 7.4 or earlier version and enable debug log and check what’s causing the issue and fix the code.
Disable Themes and Plugins on WordPress
Most of the time, after updating php 8 on WordPress website this the issue is with Plugins or themes on your wordPress website and you need to enable debug mode on wordpress which will display which plugin is causing error and once you identify the plugin then go ahead and disable plugin and your wordpress will be up and running.
Problem with Theme
If you have installed theme on wordpress and update php 8 then theme files also cause wordpress website not to work on php 8 update and you need to disable them and check if the issue is with theme or not and if theme is causing wordpress website to break after updating php 8 then you need to fix theme files and write compatible code with php 8 and then update php on wordpress.
Use Plugins and Theme Compatible with PHP 8
If you are planning to update php 8 on WordPress then you need to make sure that your php code is compatible with the new version of php 8 and update php and if plugins and themes have outdated code then it will break your WordPress website.