place this code in .htaccess under the root directory of your site
Options -MultiViews
RewriteEngine ON
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule (.+) /$1/index.php [QSA,L]
RewriteCond %{DOCUMENT_ROOT}/$1.php -f
RewriteRule ^(.+?)/?$ /$1.php [QSA,L]