How to impersonate webserver process

Question

I have this scenario:
I have a MacMini Server Late 2012 with several virtual machines using Parallels 9.  Parallels comes with a command line utility called "prlctl" that allows me to start, stop, suspend, resume any virtual machine.
I am trying to create a webpage that allows remote users to:
1) See a list of all available VMs with its status (online, stopped, suspended, active)
2) Start/Resume an specific VM
3) Stop/Suspend an specific VM
To do this I am using:
1) OSX bultin webserver
2) PHP
I created a simple PHP page to test the viability of my idea:
$out = array();
exec("prlctl list -a", $out, $r);
echo "<pre>";
for ($i=0; $i<count($out); $i++) echo "<br>".$out[$i];
echo "</pre>";
but when I access the page all I got is this:
UUID                                    STATUS       IP_ADDR         NAME
when I run that same command from command line I got:
UUID                                    STATUS       IP_ADDR         NAME
{d33828f3-326d-4e5b-9c22-9d85b86869e6}  running      -               tmicl.cwy.qas
{f91412b0-d75c-4e52-827f-3a9b7f11b140}  running      -               tmicl.dmo.prd
{895bc08f-a2e5-454d-97f8-f25b06720e55}  running      -               tmicl.pet.qas
{02c8adcc-f21a-461c-beb6-ba6ae17b1bdd}  running      -               tmicl.sql.qas
As far as I can see, the problem is caused by the user under witch the command is being executed.  When executed from the PHP page, the _www user is used and this user seems to have no access to the Parallels Service.  When ran from the command line, it ran under my local user and therefore I get the expected result.
Because of this, I need a way to impersonate the webserver process but ONLY for an specific virtual directory.  Is there a way to accomplish this, maybe using a .htaccess file ?
TIA
Victor Espina

Answer 1

I just found the solution following this post:
1) Added this lines to sudoers file:
myuser ALL=(ALL) NOPASSWD: /usr/bin/prlctl
_www ALL=(ALL) NOPASSWD: /usr/bin/prlcl 
2) The EXEC() command in PHP was changed to:
exec("sudo -u myuser prlctl list -a", $out, $r);
The basic trick is to allow your user (and the _www user) to run the specific command by sudo.
Victor Espina