Install brew first, then type below:
$ brew tap homebrew/versions
$ brew install mysql55
// unlink old mysql
$ brew unlink mysql
// new link for the 55 version
$ brew link --force mysql55
Install brew first, then type below:
$ brew tap homebrew/versions
$ brew install mysql55
// unlink old mysql
$ brew unlink mysql
// new link for the 55 version
$ brew link --force mysql55