Why isn't my .htaccess 301 redirect rule working?

I use URL rewriting on my redesigned website to give my pages tidier URLs.

RewriteEngine On

RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^$ index.php [L]

RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^.+/$ %{REQUEST_URI}index.php [L]

RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^(.+\.php|(.+/)?index)$ - [R=404,L]

RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{SCRIPT_FILENAME}.php -f
RewriteRule ^(.+)$ $1.php [L]

This .htaccess file allows /filename to actually point to /filename.php. It all works fine.

However, I have now realised that I should set up 301 permanent redirects, so that the pages of the old website (before the redesign) can redirect to pages on the new site (for SEO and linking reasons). The pages have been reorganised, so multiple old pages will redirect to new pages, for example.

The old website did not use URL rewriting. Therefore, I want to create permanent redirects such as /about-page.php to /about, doing them manually with one rule per old page.

I have tried several things, such as...

RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^about-page.php$ about [R=301,L]

...or...

Redirect 301 /about-page.php /about

...but it always ends up either not working at all (giving me a 404 error when I attempt to access /old-filename.p开发者_开发知识库hp, or breaks everything with internal server errors. It seems to work fine if I use Redirect 301 /about-page.html /about instead, but unfortunately the old URLs used .php extensions, not .html extensions.

I believe the problem is related to one of the other rules, which redirect requests for /xyz to /xyz.php, possibly creating some endless loop. But I can't figure out how to fix it.

Any advice? Thank you very much.

---

Edit: Final, working .htaccess file:

DirectoryIndex index.php #

RewriteEngine On

# -- Use a permanent redirect to point the old page to the new page.
# -- The RewriteCond is needed, or a redirect loop happens in certain cases.
# -- The full URL seems to be needed, or it redirects incorrectly.
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^about-page.php$ http://www.mywebsite.com/about [R=301,L]

# -- Redirect most other .php files to a 404 error, to avoid duplicate content.
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule ^(.+\.php|(.+/)?index)$ - [R=404,L]

# -- Redirect requests without an extension, but for a valid file, to that file.
# -- I'm not sure what the RewriteCond lines are for, but they both seem necessary.
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteCond %{SCRIPT_FILENAME}.php -f
RewriteRule ^(.+)$ $1.php [L]

---

DirectoryIndex index.php # -- this sets index.php to be default file for a folder

RewriteEngine On

# -- RewriteRule ^(.+\.php|(.+/)?index)$ - [R=404,L]
# -- dude this above line redirects all php files to 404 error
# -- so delete this, its a problem not solution

RewriteCond %{SCRIPT_FILENAME}.php -f
RewriteRule ^(.+)$ $1.php [L]

RewriteRule ^about-page.php$ /about [R=301,L]

This should work, comment if problem occurs