Mod Rewrite Htaccess for Fake Directories - php

Question

I am trying to create fake directories to redirect specific parameters to specific subdirectories as such:
From: www.example.com/username
To: www.example.com/posts?uid=alex
From: www.example.com/p/1234
To: www.example.com/posts?url=1234
It is somehow more complicated example from the rest questions with the same subject on stackoverflow and most answers do not give an explanation on how it works, thus I am not able to come into a conclusion on how I could solve this.

Answer 1

Try:
RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^p/([^/]+)$ /posts?url=$1 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^([^/]+)$ /posts?uid=$1 [L]
First, you need to make all of your links look like this:
www.example.com/username
www.example.com/p/1234
The rewrite rules above will match the /p/1234 (via ^p/([^/]+)$) and /username (via ^([^/]+)$) and internally rewrite them to the /posts URI. Note that this will not change the URL in the browser's location bar, as that is an external redirect. If someone enters www.example.com/posts?uid=alex, the URL will be unchanged.

Answer 2

Enable mod_rewrite and .htaccess through httpd.conf and then put this code in your DOCUMENT_ROOT/.htaccess file:
Options +FollowSymLinks -MultiViews
# Turn mod_rewrite on
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^p/([^/]+)/?$ /posts?url=$1 [L,QSA,NC]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/?$ /posts?uid=$1 [L,QSA,NC]