500 Internal Server Error is a general response from the server that something has gone wrong. To solve it properly we suggest enabling error display first. This way you will see the real error.
If nothing changed and you still see the error 500 after enabling PHP errors display, try changing PHP version and enabling display_errors on different versions. Once that’s done you can proceed with the suggestions below:
If you are using WordPress
In case you got a WordPress website, you can refer to this comprehensive tutorial: How to Fix 500 Internal Server Error on WordPress
Any other website
Based on error you see:
Call to undefined function - change your PHP version, try all available versions. Do a code-review
Parse error (Syntax Error) - check the file mentioned in the error to see if you can find any syntax errors
Warning Access Denied - double-check database credentials, which you inserted in your configuration file
Fatal error, Failed opening required - means that your site is calling for the file that does not exist – or cannot be executed. Check if the file, mentioned in the error, exists
Depreciated - lower your PHP version. You might need to try all versions before you find the one that suits your website
In case you tried the steps and the website still doesn’t work - we highly suggest restoring your website from a backup 😊