watir-webdriver在调用时无法正常工作

I have a PHP script that calls a Ruby script (system('ruby /lib/program.rb')) that requires watir-webdriver. The system it's on has ruby version

ruby 2.0.0p648 (2015-12-16 revision 53162) [x86_64-linux]

and when I check the error logs I have this message

/usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require': cannot load such file -- watir-webdriver (LoadError)
    from /usr/lib/ruby/1.9.1/rubygems/custom_require.rb:36:in `require'
    from /lib/program.rb:4:in `<main>'

Requiring rubygems above does nothing. How can I fix?

See here for output when I run "by hand" and not via PHP's system function:

https://gist.github.com/anonymous/ad7befc4ca188e7b3989d6d023bcf100

require_relative may solve requiring package. Try this:

require_relative 'watir-webdriver'

Try doing system('rvm use 2.0') before executing the ruby script. That should ensure that the shell is using the correct version for the Ruby execution.