.htaccess code
Edit your public_html/.htaccess file and enter the appropriate code on a new line.
Do NOT refer to the file name. Rather, refer to the directory where the file exists.
E.g. If you want to use "/home/username/www/folder/php.ini", type:
<IfModule mod_suphp.c>
suPHP_ConfigPath /home/username/www/folder
<Files php.ini>
order allow,deny
deny from all
</Files>
</IfModule>
suPHP_ConfigPath /home/username/www/folder
<Files php.ini>
order allow,deny
deny from all
</Files>
</IfModule>
Save your .htaccess file and enjoy.
If you don't use this option, PHP will use its default path.