How Do I Fix a 500 Internal Server Error?

Hello. I'm using "been-there.us" domain.
And I developed ios app with file upload feature, But it receives "An error was encountered while processing your request. Typically this is a temporary condition. Please contact the web site owner for further assistance.". Current web server is codeigniter based and is works well on localserver.
But on your domain, it occurs 500 error. please modify my php.ini to enable error_log.
Thank you.