RewriteEngine on
RewriteCond %{REQUEST_FILENAME} !\.(js|css|gif|jpg|jpeg|png|ico|swf|pdf)$
RewriteCond %{REQUEST_URI} !=/
RewriteRule ^(.*)$ / [L,R=301]

Redirects all requests to the index page, unless the file is an asset (css, javascript, image, etc). All directories (real or fake) get redirected to the index page. Note the file extensions (js|css|gif|jpg|jpeg|png|ico|swf|pdf) can be added and subtracted too, depending on your needs.

htaccess redirect all pages to index page

PHP