How to remove preinstalled Apache and PHP from Mac OS Sierra
Removing system macOS binaries is not a good idea, they will be reinstalled during a next system upgrade and they could be needed by some system scripts.

To enable the homebrew php from the command line, read the output of brew info php70:


  If you wish to swap the PHP you use on the command line, you should add the following to ~/.bashrc, ~/.zshrc, ~/.profile or your shell's equivalent configuration file:
    export PATH="$(brew --prefix homebrew/php/php70)/bin:$PATH"


If you have installed php 7.2, check the output of brew info php72.