Fatal errror when installing freePBX

I am trying to install freePBX on Archlinux, everying seems OK but I got this fatal error when running install_amp:

Warning: require_once(/home/httpd/html/admin/functions.inc.php): failed to open stream: Permission denied in /var/lib/asterisk/bin/retrieve_conf on line 183

Fatal error: require_once(): Failed opening required ‘/home/httpd/html/admin/functions.inc.php’ (include_path=’.:/usr/share/pear:/var/lib/asterisk/bin/’) in /var/lib/asterisk/bin/retrieve_conf on line 183

How can I fix this error??