I noticed a typo in the original answer, but it did work for me in my .zshrc file. The typo was the end of the last line, it was missing the final / between the php version and bin directory
#MAMP Madness
export PATH=/Applications/MAMP/Library/bin:$PATH
PHP_VERSION=`ls /Applications/MAMP/bin/php/ | sort -n | tail -1`
export PATH=/Applications/MAMP/bin/php/${PHP_VERSION}/bin:$PATH