RewriteEngine on
RewriteCond %{THE_REQUEST} /([^.]+)\.php [NC]
RewriteRule ^ /%1 [NC,L,R]
RewriteCond %{REQUEST_FILENAME}.php -f
RewriteRule ^ %{REQUEST_URI}.php [NC,L]

ErrorDocument 403     /cgi-sys/403_def.html

ErrorDocument 404     /cgi-sys/404_def.html

ErrorDocument 500     /cgi-sys/500_def.html

ErrorDocument 502     /cgi-sys/502_def.html

ErrorDocument 503     /cgi-sys/503_def.html

ErrorDocument 504     /cgi-sys/504_def.html