How to implement URP in PHP using a cancan-style interface

cancan.php

<?php

class User
{
  public $admin;
  public $roles = array();

  function roles()
  {
    if (isset($this))
    {
      return $roles;
    }
    else
    {
      return array('admin', 'manager', 'rep', 'customer', 'user');
    }
  }

  function has_role( $needle )
  {
    foreach ($this->roles as $role)
    {
      if($role == $needle)
      {
        return true;
      }
    }
    return false;
  }

  function can_view($entity)
  {
    if( $this->has_role('admin') )
    {
      return true;
    }
    else
    {
      if( $entity == "thing" && $this->has_role('manager') )
      {
        return true;
      }
      else
      {
        return false;
      }
    }
  }

  function can_edit($entity)
  {

  }

  function can_delete($entity)
  {
    return false;
  }

  function can_manage($entity)
  {
  }

}

$a = new User();
if( $a->can_view('whatever') )
{
  echo "yep\n";
}
else
{
  echo "as expected, non-admins can't view random stuff\n";
}

array_push($a->roles, 'admin');

if( $a->can_view('whatever') )
{
  echo "as expected, admins can view anything.";
}
else
{
  echo "uh oh";
}

?>

@mustmodify thanks for this, and I should say, writing more Ruby is making me like PHP more -- just saying.