What role does the file extension (.php4) play in PHP interpretation by the web server?

The file extension (.php4) indicates to the web server that the file should be interpreted as PHP code. If the web server is not configured to recognize this file extension, it may not process the PHP code correctly. To solve this issue, you can update the web server configuration to include .php4 as a valid PHP extension. ```apache AddType application/x-httpd-php .php4 ```