The following step(s) will help protect your config.php used by VBulletin even if php stops working.

1) This step might be optional for most. Since I do not use .htaccess files "normally", in my sites configuration file (that is then included in the http.conf for Apache).
I added the directives:
<Directory "E:/DomZeus/sitebuddycom/wwwroot/board/includes">
AllowOverride FileInfo Options Limit
</Directory>

This will enable .htaccess in that folder and permit the usage of "order" directive.

2) Then create a .htaccess file in the "includes" folder with:
<Files config.php>
order deny,allow
deny from all
</Files>