Redirect request and hide .php extension from the request - apache

Question

We have started to change our website, and we use the old and the new site together. If something not exist on the new site we just redirect them back to the old one. (This is a transparent process for the user.)
This is how .htaccess rules looks like now:
RewriteEngine On
RewriteBase /
RewriteCond %{http_host} ^domain.hu [NC]
RewriteCond %{http_host} !^domain.hu.data18.websupport.sk$ [NC]
RewriteRule ^(.*)$ http://www.domain.hu/$1 [R=301,NC,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/static-old%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/static-old%{REQUEST_URI} -d
RewriteRule ^(.*)$ /static-old/$1 [QSA]
RewriteRule ^(.*)\.html$ $1.php [L,R=301,QSA]
So if we don't find the the file on the main directory, but we find it in the old one we serve the old one instead of a 404. And if the requested file has html extension then we rewrite it internally to php, because we changed this a while ago.
I want to hide the php extension (and so html will be hidden too) so if a requested uri is /something.php or /something.html then only show /something to the user. But I if I edit .htacces like this:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/static-old-from-seocms%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/static-old-from-seocms%{REQUEST_URI} -d
RewriteCond %{REQUEST_URI} ^(.*?)\.php[\s?] [NC]
RewriteRule ^/%1/ [R=301,L,NE]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/static-old-from-seocms%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/static-old-from-seocms%{REQUEST_URI} -d
%{REQUEST_URI} !\.(.*)$
RewriteRule ^(.*)$ $1.php [L,R=301,QSA]
RewriteRule ^(.*)$ /static-old-from-seocms/$1 [QSA,L]
I will get an 500 internal server error, the .htaccess parsing fail.
I think this script will check if the requested file has php extension and does not exist in the main directory then redirect it to the same address without the php extension, after that the script will check if the requested uri is not exist in the main directory and does not have an extension then write it a php extension to it internally.

Answer 1

Try this .htaccess:
RewriteEngine On
RewriteBase /
RewriteCond %{http_host} ^domain\.hu [NC]
RewriteCond %{http_host} !^domain\.hu\.data18\.websupport\.sk$ [NC]
RewriteRule ^(.*)$ http://www.domain.hu/$1 [R=301,L]
RewriteCond %{THE_REQUEST} \s/+(.+?)\.(php|html)[\s?] [NC]
RewriteRule ^ /%1 [R=301,L,NE]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^.]+)/?$ /$1.php [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{DOCUMENT_ROOT}/static-old%{REQUEST_URI} -f [OR]
RewriteCond %{DOCUMENT_ROOT}/static-old%{REQUEST_URI} -d
RewriteRule ^(.+)$ /static-old/$1 [L]