Javascript-ajax successfully returned JSON data, but was prompted with a 500 error.

Using AJAX to request data asynchronously, the data has been successfully returned but the browser prompts a 500 error.

Test succeeded on localhost. However, an error occurred after uploading to the Ubuntu virtual machine.

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Using AJAX to request data asynchronously, the data has been successfully returned but the browser prompts a 500 error.

Test succeeded on localhost. However, an error occurred after uploading to the Ubuntu virtual machine.

The front-end code does not see anything.

500 is a syntax error in the code, it should be a syntax error in admin.php

Compare requests in both local and Ubuntu 2 environments first
But I think it's your local environment and the environment in Ubuntu caused some grammatical errors, including PHP version and Apache (Nginx)

The backend program starts with these aspects: 1. Returned data format error 2. Procedural error 3. Server-side error,

See if there's a problem with the path to PHP? See if the returned data is complete?

It is recommended that all errors be turned on.
For example, code open Error alert:

Then remember to check the PHP error log.
Nginx error Log
Error log for PHP-FPM
In some cases, I reported a 50x error. The system is not prompted. Is logged in the error log. Take a closer look at yourself.

Server environment is caused by the majority of the reasons, Ubuntu, check the permissions it. In addition to the landlord to make a suggestion. Local development. It's best to use vagrant or Docker to build your development environment. Wamp and other integrated environments for learning

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