htaccess rewrite to a script when the requested file does not exist - php

Question

I hope you can help. I'm trying to write a .htaccess file to do the following.
redirect to www. address
remove .php from URL
If the file doesn't exist then use filechecker.php?page=filename
#1 I can do with
RewriteCond %{HTTP_HOST} ^example.com$
RewriteRule (.*) http://www.example.com/$1 [R=301,L]
#2 I can do with
RewriteCond %{SCRIPT_FILENAME}.php -f
RewriteRule [^/]$ %{REQUEST_URI}.php [QSA,L]
#3 I thought
RewriteCond %{REQUEST_FILENAME}.php !-f
RewriteRule ^([^/]*)$ filechecker.php?page=$1 [QSA,L]
would work, but for some reason it is ignoring the fact that the page does actually exist.

Answer 1

Your solution for 2 will loop, but simple enough to fix, stick something along the following lines in your file for part 2 and 3:
#If the Browser request contains a .php, instruct the browser to remove it.
RewriteCond %{THE_REQUEST} \.php [NC]
RewriteRule ^/?(.*)\.php$ http://%{HTTP_HOST}/$1 [R=301,NC,L]
#If a request is received for a non file-system object, that doesn't have a .php suffix, then store the full path, filename, and URI in a variables with that extention.
RewriteCond %{SCRIPT_FILENAME} !-d
RewriteCond %{SCRIPT_FILENAME} !-s
RewriteCond %{SCRIPT_FILENAME} !-f
RewriteCond %{SCRIPT_FILENAME} !^\.php$ [NC]
RewriteRule ([^/]+)$ - [E=testScript:%{SCRIPT_FILENAME}.php,E=testFile:$1.php,E=testURI:%{REQUEST_URI}.php]
#See if the file exists with a .php extention, if it does internally rewrite
RewriteCond %{ENV:testScript} -s [OR]
RewriteCond %{ENV:testScript} -f
RewriteRule .* %{ENV:testURI} [L]
#Else if a ENV:testDile is set, then pass the name to the php script
RewriteCond %{ENV:testFile} !^$
RewriteRule .* /filechecker.php?page=%{ENV:testFile} [L]
FYI: The Apache mod_rewrite documentation is worth a read, if your unclear as to what the above rules do, or if you want something a little more abstract consider the following post.