Redirect from HTTP to HTTPS.

.htaccess

# Reference: Apache Module mod_ssl
# http://httpd.apache.org/docs/current/mod/mod_ssl.html

<IfModule ssl_module>

# Reference: Apache Module mod_rewrite
# http://httpd.apache.org/docs/current/mod/mod_rewrite.html

<IfModule rewrite_module>
RewriteEngine on
RewriteCond %{HTTPS} off
RewriteRule ^(.*)$ https://%{SERVER_NAME}%{REQUEST_URI} [R,L]
</IfModule>

<IfModule !rewrite_module>
ErrorDocument 403 "Access here via the HTTPS protocal."
SSLRequireSSL
</IfModule>

</IfModule>

<IfModule !ssl_module>
ErrorDocument 403 "The module ssl_module is required."
Deny from all
</IfModule>

HTTP_HOST vs. SERVER_NAME