For PHP alternatives to RVM and rbenv, you have phpbrew, phpenv and php-version. Please be aware that I am the author of php-version so of course I prefer it as I wrote it to scratch my own itch (I wanted something minimal with command completion); however, phpenv is quite good as well. You would do well to use either.
On OS X, you can install a PHP version manager using Homebrew.
First, add the PHP formulae for homebrew:
% brew tap homebrew/homebrew-php
Then, using the formulae installed from homebrew-php you can install either with:
% brew install php-version
or
% brew install phpenv
The php-version README.md lists a few more alternatives so you might want to have a look.
BTW, I would consider php-version to be more aligned with chruby in that it tries to do one thing well.