composer installでエラーが出たので対応した．zmqのプラグインがなかった．

# composer installでエラーが出たので対応した．zmqのプラグインがなかった．

$ composer install --no-scripts
> You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
> Loading composer repositories with package information
> Installing dependencies (including require-dev) from lock file
> Your requirements could not be resolved to an installable set of packages.

> Problem 1
> - react/zmq v0.3.0 requires ext-zmq * -> the requested PHP extension zmq is missing from your system.
> - react/zmq v0.3.0 requires ext-zmq * -> the requested PHP extension zmq is missing from your system.
> - Installation request for react/zmq v0.3.0 -> satisfiable by react/zmq[v0.3.0].

$ brew unlink php71
$ brew link php56
$ php artisan optimize