1. Copy original (default) CPanel php.ini file from location: /usr/local/lib/php.ini to your account folder: /home/account_username/path_to_php_ini/
2. Add the following code to the .htaccess file within your account’s public_html folder: suPHP_ConfigPath /home/account_username/path_to_php_ini/
   
3. Change this php.ini file to suits your needs and That’s all folks!

Note:
replace everywhere ‘/home/account_username/path_to_php_ini/‘ with the appropriate path to your custom php.ini file)