Drush does not work after I sudo su to another user

Question

I have a CentOS 6 server with WHM/cPanel. I installed a global Drush as root using the instructions here (http://docs.drush.org/en/master/install/). Drush works fine for any user I ssh in as. However I typically ssh in as my user and then sudo su to the user I'm working on. When I do that I get these errors. If I ssh in as that user directly drush works fine. How can I make drush work when I su to a different user?

PHP Warning:  proc_open(): Descriptor item must be either an array or a File-Handle in phar:///usr/local/bin/drush/includes/startup.inc on line 366
Content-type: text/html; charset=UTF-8

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<b>Warning</b>:  proc_open(): Descriptor item must be either an array or a File-Handle in <b>phar:///usr/local/bin/drush/includes/startup.inc</b> on line <b>366</b><br />
PHP Warning:  proc_get_status() expects parameter 1 to be resource, boolean given in phar:///usr/local/bin/drush/includes/startup.inc on line 367
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<b>Warning</b>:  proc_get_status() expects parameter 1 to be resource, boolean given in <b>phar:///usr/local/bin/drush/includes/startup.inc</b> on line <b>367</b><br />
PHP Warning:  proc_close() expects parameter 1 to be resource, boolean given in phar:///usr/local/bin/drush/includes/startup.inc on line 368
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<b>Warning</b>:  proc_close() expects parameter 1 to be resource, boolean given in <b>phar:///usr/local/bin/drush/includes/startup.inc</b> on line <b>368</b><br />

EDIT

So I got it to work. If I do sudo su - newuser instead of sudo su newuser it works.

I think it's related to CLI/CGI. PHP runs as CLI when I su with the - and CGI when I su without the -. Can anyone explain the difference the - makes?

Answer 1

Found the answer here: https://superuser.com/questions/453988/whats-the-difference-between-su-with-and-without-hyphen

The difference between "-" and "no hyphen" is that the latter keeps your existing environment (variables, etc); the former creates a new environment (with the settings of the actual user, not your own).