RewriteCond %{ENV:HTTPS} on
# Проверяем наличие https в URL.
RewriteRule ^.*$ http://%{SERVER_NAME}%{REQUEST_URI} [R=301,L]
# Перенаправляем протокол на http.
RewriteCond %{REQUEST_METHOD} =GET
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME}\.php -f
RewriteCond %{REQUEST_URI} ^(.+)\.php$
RewriteRule ^(.*)$ %1/ [R=301,L]
RewriteCond %{QUERY_STRING} (^|&)art_id\=10($|&)
RewriteRule ^article$ /article\?id=10 [L,R=301]
RewriteCond %{QUERY_STRING} (^|&)art_id\=([0-9]{1,})($|&)
RewriteRule ^article$ /article\?id=%2 [L,R=301]