Exec ruby cmd error with PHP

Here is my environment.

• PHP version: 5.5.23
• Framework: fuelPHP
• Ruby: 2.3.0

My Ruby script requires aws-sdk. I want to call ruby script as it works on Putty, for example like this:

ruby filelist.rb

I tried it giving absolute path for Ruby and the script file. It works on Putty, but not when I call it from PHP. I get this error:

/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require': cannot load such file -- aws-sdk-s3 (LoadError)
    from /usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/site_ruby/2.3.0/rubygems/core_ext/kernel_require.rb:55:in `require''

Please help me.

This is a solution. It's in Japanese, but you can translate it to read.