How to install php7 modules in archlinux?

Ok, here it is answered by pierre schmitz, thx nymous for the link:

openssl, phar and posix modules are now built in php7 core. Remove the corresponding directives from your php.ini, e.g. ;extension=openssl.so.

php-xcache is incompatible with php7, remove package, the project seems dead.

full list of 3rd party package status:

| Package          | Status       | Solution                                                     |
|------------------|--------------|--------------------------------------------------------------|
| graphviz         | incompatible | remove PHP bindings                                          |
| php-apcu         | compatible   | update to version 5                                          |
| php-geoip        | incompatible | remove package                                               |
| php-memcache     | incompatible | remove package, project seems dead                           |
| php-memcached    | incompatible | remove package, move back when upstream version is available |
| php-mongo        | incompatible | remove package, superseded by the mongodb driver             |
| php-xcache       | incompatible | remove package, project seems dead                           |
| uwsgi-plugin-php | incompatible | remove PHP support, upstream update seems possible           |
| xdebug           | compatible   | update to latest release candidate of version 2.4            |