RewriteEngine On

# browser requests PHP
RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^\ ]+)\.php
RewriteRule ^/?(.*)\.php$ /$1 [L,R=301]

# check to see if the request is for a PHP file:
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteRule ^/?(.*)$ /$1.php [L]