RewriteEngine On

# If requested resource exists as a file or directory, skip next two rules
RewriteCond %{DOCUMENT_ROOT}$1 -f [OR]
RewriteCond %{DOCUMENT_ROOT}$1 -d
RewriteRule (.) - [S=2]
#
# Else rewrite requests for non-existent resources to index.php
RewriteRule (.) index.phpq=$1 [L]