There are no Homebrew formulas for different PHP versions anymore
It seems Homebrew significantly changed everything related to PHP recently. Here is what it outputs if you try to install zeroc-ice/tap/php70-ice (as suggested on https://zeroc.com/downloads/ice#macos page):
zeroc-ice/tap/php70-ice was deleted from zeroc-ice/tap in commit bb34b8f: Remove dependency on deprecated homebrew-php - Removed php56-ice, php70-ice, and php71-ice which depended on homebrew/php - Added php-ice which depends on homebrew/core/php See https://brew.sh/2018/01/19/homebrew-1.5.0/ for more information on the deprecation of homebrew-php.
So I guess that section on a download page has to be updated at least.