Use .htaccess to rewrite address from xxx.example.com to example.com/xxx/ - apache

Question

I am looking for a way so that users can access their page by typing xxx.example.com and are then forwarded to their respective WordPress post.
Now I already have two rewrite functions on my site: (not written by me)
To use https everywhere:
#Rewrite everything to https
RewriteEngine On
RewriteCond %{HTTPS} !=on
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=302]
And the WordPress:
# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress
Now, that WordPress function seems to translate example.com/post_title to the corresponding post.
But how do I rewrite it so it translates post_title.example.com to the corresponding post?
And if possible, still showing the xxx.example.com instead of example.com/xxx

Answer 1

The following should work, change your .htaccess to:
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
# Rewrite to https
RewriteCond %{HTTPS} !=on
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=302]
# This rewrite rule will only be used if
# we have an empty query string and the http host does not start with www
RewriteCond %{QUERY_STRING} ^$
RewriteCond %{HTTP_HOST} !^www\.example\.com
RewriteCond %{HTTP_HOST} ^(.*)\.example\.com
RewriteRule ^$ http://%{HTTP_HOST}/%1 [L]
# The default wordpress rewrite rule
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
For this to work I guess you need to setup a correct permalink structure in your wordpress installation: