Heroku php and nodejs in the same app

I'm using a node package called exec-php to execute php functions within nodejs app.

I would like to push that app to Heroku, but I'm wondering how to make that and how would be the PHP bin locally i'm using /Applications/MAMP/bin/php/php7.0.0/bin/php what would be the path to php bin in Heroku

I tested vendor/bin/heroku-php-apache2 but it doesn't work, so what would be the path to php binary in heroku