Install php for OSX Sierra or higher version

# clean old version if using brew
brew uninstall [email protected]
# php>7.3 some extensions like mcrypt won't work
brew install [email protected] 

# edit php path
open ~/.zshrc

# add lines
# PHP Path
export PATH="/usr/local/opt/[email protected]/bin:$PATH
export PATH="/usr/local/opt/[email protected]/sbin:$PATH

# and also make sure your brew $PATH before your default $PATH in ~/.bash_profile 
# For example⬇️ this might different depends your brew prefix path
# Brew Path
export PATH=/usr/local/bin:$PATH
# Default
export PATH=/usr/bin:/usr/sbin:/bin:/sbin:$PATH

# install extensions
sudo pecl install mcrypt-1.0.1

libmcrypt prefix? [autodetect] :  yes
php -i | grep "mcrypt"

pecl install memcached
#"yes" to libmemcached