PHP errors are by default set to go to the apache error log. On Ubuntu, the error log is located at /var/log/apache2/error.log. If you are a PHP developer, it is good idea to open a small terminal window and type the following:

tail -f /var/log/apache2/error.log

This would essentially give you a live view of the error log. As you generate errors, you would see the error messages on the terminal.

Displaying errors in browser
To display errors in your browser, open php.ini file for editing. Find "display_errors" and set it to "on".