Final answer:
In PHP, the direct way to change default error reporting is by using the error_reporting() function. Alterations can also be made to the php.ini file or the .htaccess file for server-wide or directory-specific changes. The set_error_handler() function is related but serves a different purpose.
Step-by-step explanation:
In PHP, you can change the default error reporting by using several methods. The most direct method is C) Using the error_reporting() function. This function allows you to set the level of error reporting at runtime. For example, if you want to report all errors except notices, you would use error_reporting(E_ALL & ~E_NOTICE);. If you want to turn off error reporting completely, you could use error_reporting(0);.
Option B) Modifying the php.ini file is another way to change the default error reporting. In the php.ini file, you can set the error_reporting directive to the desired level. This change will affect all scripts running on the server.
Lastly, option D) Changing the error_reporting configuration in the .htaccess file is a method used on Apache servers. You can use the php_value error_reporting directive to set the level of error reporting for scripts running in a specific directory.
While set_error_handler() is related to error handling in PHP, it does not directly change the default level of error reporting, but instead sets a custom error handler function.