The solution with mod_proxy_fcgi and mod-fpm seems to have serious problems with providing a correct environment for php, e.g the bug
https://bugs.php.net/bug.php?id=65641seems to be still unresolved. Also you can find a lot of comments in the mod-fpm sources which point to apache-specific problems (for an example see below). 
So I'm not sure whether it's really a good idea to include these packages in the archlinux distribution. At least the default configuration for normal LAMP-users should omit mod-fpm and provide other ways to support apache for php. Since I'm not an LAMP-expert I'm not sure whether returning to the single threaded model for apache 2.4 is really the better option than returning to apache 2.2.
-------------------------------------------------------------------------------------------------------------------------
in the mod-fpm sources I've found the comment with different to bug references.
#define APACHE_PROXY_FCGI_PREFIX "proxy:fcgi://"
		/* Fix proxy URLs in SCRIPT_FILENAME generated by Apache mod_proxy_fcgi:
		 *     proxy:fcgi://localhost:9000/some-dir/info.php/test?foo=bar
		 * should be changed to:
		 *     /some-dir/info.php/test
		 * See: 
http://bugs.php.net/bug.php?id=54152		 *      
https://issues.apache.org/bugzilla/show ... i?id=50851		 */