Assistance with .htaccess - mod-rewrite

Question

I need the .htaccess file to allow all file and directories if they exist, but php extensions are not needed for existing files and everything else goes to the index file.(MVC type processing) I've tried a few things, but haven't got it right yet.
Examples:
www.example.com/search/
file exists as search.php and should display the file
www.example.com/shopping/mylist/file doesn't exist so should go to index.php
RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ $1.php [L]
RewriteRule ^(.+)$ index.php?url=$1 [QSA,L]

Answer 1

mod_rewrite is highly order dependent so let's think through it logically from most specific to least specific.
You will need a condition to check for the existence of the .php file based on a match from the () group in RewriteCond first. That will be two conditions followed by a RewriteRule to actually direct it into the .php file. Your example /search/ has a trailing slash, and that's why we'll first need to capture it as %1 with two RewriteCond. Otherwise, I would probably use %{REQUEST_FILENAME}.php -f to test if it exists. This sort of explains how the %1 backreference can be used in RewriteCond chain.
Then after applying that one to attempt to match a .php file, use the more generic index.php rule as you already have it, together with the two conditions to check whether the file actually exists.
RewriteEngine On
# Match an optional trailing slash on the filename
# and capture it as %1
RewriteCond %{REQUEST_FILENAME} ^(.+)/?
# And test if the match (without /) has a .php file
RewriteCond %1.php -f
# Rewrite everything up to an optional trailing /
# matched in the first RewriteCond
# into its .php suffix (add QSA to retain query string)
# It isn't necessary to give a full regex here since %1
# already contains everything needed
RewriteRule ^ %1.php [L,QSA]
# Now with that out of the way, apply the generic
# rule to rewrite any other non-existing file to index.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
# I used * instead of + so it also matches an empty url
RewriteRule ^(.*) index.php?url=$1 [QSA,L]
I have successfully tested this setup in a temporary directory. It appears to meet your requirements.