sh: 1: ruby: not found when i am executing ruby from browser - ruby

Question

I am creating a PHP website which have to execute a ruby command from terminal for that i am using :-
1)
$output = shell_exec('ruby emailConverter.rb 2>&1');
var_dump($output);
This throws the error
string(23) "sh: 1: ruby: not found"
or
2)
exec("ruby emailConverter.rb", $output, $return);
var_dump($output);
UPDATE
AFTER doing this as #psal suggested
$path = '/home/vishal/.rvm/rubies/ruby-2.1.2/bin/ruby'
$output = shell_exec($path.' emailConverter.rb 2>&1');
var_dump($output);
getting this error
string(308) "/home/vishal/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in require: cannot load such file -- premailer (LoadError)
from /home/vishal/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/rubygems/core_ext/kernel_require.rb:55:in require'
from emailConverter.rb:4:in `<main>'
but when i execute this any of the above command(1 and 2) directly from terminal, it works fine...
what is the problem with that?
Any help?

Answer 1

In my case,
I added
#!/usr/bin/env /usr/local/rvm/wrappers/ruby-2.4.1/ruby
on top of the ruby script file.
ie:
#!/usr/bin/env /usr/local/rvm/wrappers/ruby-2.4.1/ruby
require 'jwt'
...

Answer 2

As #simonwo said, this error happend because Ruby is not in your PATH. Find the ruby binary using which then add it to your script. Usually it's in /usr/bin/.
Example on Ubuntu :
$ which ruby
/usr/bin/ruby
Once you have the path, add it to your shell_exec :
$rubyBin = '/usr/bin/ruby';
shell_exec("$rubyBin emailConverter.rb 2>&1");
// or
exec("$rubyBin emailConverter.rb", $output, $return);