How can PHP functions be disabled to prevent unauthorized file manipulation on a server?

To prevent unauthorized file manipulation on a server, PHP functions can be disabled by using the `disable_functions` directive in the php.ini file. This directive allows you to specify a list of functions that should be disabled for security reasons. By disabling potentially harmful functions, you can help protect your server from unauthorized access or file manipulation.

// Disable specific PHP functions to prevent unauthorized file manipulation
ini_set('disable_functions', 'exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source');