require 'rubygems'
require 'net/ssh'

host = "abc.de"
user = "user_xy"
pass = "user_pass"

begin
    Net::SSH.start(host, user, :password => pass) do |ssh|
        $a = ssh.exec! "cd xy_dir && php abc.phar do_this"
        ssh.close
        puts $a
end
rescue
    puts "Unable to connect to #{host}."
end