/**
* canSeeCompany() method will cache its result here (company_id => visible as bool)
*
* @var array
*/
private $visible_companies = array();

/**
* Returns true if this user can see $user
*
* @param User $user
* @return boolean
*/
function canSeeUser(User $user) {
  return $this->canSeeCompany($user->getCompany());
} // canSeeUser

/**
* Returns true if this user can see $company. Members of owener company and
* coworkers are visible without project check! Also, members of owner company
* can see all clients without any prior check!
*
* @param Company $company
* @return boolean
*/
function canSeeCompany(Company $company) {
  if($this->isMemberOfOwnerCompany()) return true;
  
  if(isset($this->visible_companies[$company->getId()])) {
    return $this->visible_companies[$company->getId()];
  } // if
  
  if($company->isOwner()) {
    $this->visible_companies[$company->getId()] = true;
    return true;
  } // if
  
  if($this->getCompanyId() == $company->getId()) {
    $this->visible_companies[$company->getId()] = true;
    return true;
  } // if
  
  // Lets companye projects for company of this user and for $company and 
  // compare if we have projects where both companies work together
  $projects_1 = DB::executeAll("SELECT `project_id` FROM " . ProjectCompanies::instance()->getTableName(true) . " WHERE `company_id` = ?", $this->getCompanyId());
  $projects_2 = DB::executeAll("SELECT `project_id` FROM " . ProjectCompanies::instance()->getTableName(true) . " WHERE `company_id` = ?", $company->getId());
  
  if(!is_array($projects_1) || !is_array($projects_2)) {
    $this->visible_companies[$company->getId()] = false;
    return false;
  } // if
  
  foreach($projects_1 as $project_id) {
    if(in_array($project_id, $projects_2)) {
      $this->visible_companies[$company->getId()] = true;
      return true;
    } // if
  } // foreach
  
  $this->visible_companies[$company->getId()] = false;
  return false;
} // canSeeCompany

<?php if(isset($online_users) && is_array($online_users) && count($online_users)) { ?>
<div class="sidebarBlock">
  <h2><?= lang('online users') ?></h2>
  <div class="blockContent">
    <p><?= lang('online users desc') ?></p>
    <ul>
<?php foreach($online_users as $user) { ?>
<?php if(logged_user()->canSeeUser($user)) { ?>
      <li><a href="<?= $user->getCardUrl() ?>"><?= clean($user->getDisplayName()) ?></a> <span class="desc">(<?= clean($user->getCompany()->getName()) ?>)</span></li>
<?php } // if ?>
<?php } // foreach ?>
    </ul>
  </div>
</div>
<?php } // if ?>