in our setup, we use mod_proxy_fcgi to talk to the php backend (fpm). for reasons of efficiency, we do not proxy all requests to fpm, only the ones that are either php, or not satisfiable by anything else. this is the common scenario in which one would use FallbackResource however, FallbackResource (as of 2.4.10) cannot be used with a proxy resource. instead, we use mod_rewrite: RewriteEngine On RewriteRule ^/.*\.php(/.*)?$ unix:///srv/web/acme.com/logs/socket|fcgi://127.0.0.1%{DOCUMENT_ROOT}$0 [P] RewriteCond %{DOCUMENT_ROOT}%{REQUEST_FILENAME} !-f RewriteCond %{DOCUMENT_ROOT}%{REQUEST_FILENAME} !-d RewriteRule ^ unix:///srv/web/acme.com/logs/socket|fcgi://127.0.0.1%{DOCUMENT_ROOT}/index.php$0 [P] and it works perfectly fine. so long as we do *not* load mod_proxy_http into the same httpd daemon. if we do, the above proxy urls will suddenly be assumed as http://. this seems… bad. and wrong.
Still seems to occur with 2.4.38, e.g. for both RewriteRule ^/redirect$ unix:/path/to/socket|fcgi://localhost/redirect.php [proxy] RewriteRule ^/redirect2$ proxy:unix:/path/to/socket|fcgi://localhost/redirect.php [proxy] These fail with 404 Not Found if mod_proxy_http.so is enabled, e.g.: The requested URL /unix:path/to/socket|fcgi://localhost/redirect.php was not found on this server. The requested URL /proxy:unix:path/to/socket|fcgi://localhost/redirect.php was not found on this server.