Ubuntu – Setting up simple vhost on lighttpd

You've a misunderstanding of how <VirtualHost > works. When using name-based virtual hosting (that is, same IP, multiple hostnames to distinct them), you need to have unique ServerNames.

Furthermore, you've set your DocumentRoot to /var/www/mwiki which causes http://localhost/ to show your wiki. Since you've one ServerName only (localhost), I suggest you to add an Alias instead of a virtual host.

<VirtualHost *:80>
    ServerName localhost
    DocumentRoot "/var/www/reviews.mysite.com/htdocs"
    AddDefaultCharset UTF-8
    Alias /mywiki /var/www/mwiki
    # ...

Virtual Hosts are only useful if you've multiple IPs or hostnames. Examples:

# Use ServerNames to distinct virtual hosts on 127.0.0.1
NameVirtualHost 127.0.0.1:80
<VirtualHost 127.0.0.1:80>
    ServerName site1.example.com
    DocumentRoot /var/www/site1.example.com
</VirtualHost>
<VirtualHost 127.0.0.1:80>
    ServerName site2.example.com
    DocumentRoot /var/www/site2.example.com
</VirtualHost>
<VirtualHost 127.0.0.2:80>
    ServerName meh.example.com
    DocumentRoot /var/www/meh.example.com
</VirtualHost>

Added to /etc/hosts:

127.0.0.1   site1.example.com
127.0.0.1   site2.example.com
# note: the next line is not included in the vhost config
127.0.0.1   invalid.example.com
127.0.0.2   meh.example.com

You can now visit the hosts using the {site1,site2,meh}.example.com domains. If you open 127.0.0.1 or invalid.example.com, the first vhost (site1.example.com) will be picked.

The solution is to make sure php has the mysql drivers installed. Code Igniter uses the @ to take control of any errors in it's sql module which means the logs will not show anything if there is an issue connecting to the database.

https://stackoverflow.com/questions/15588813/codeigniter-blank-page-and-error-500-in-apache-log