[dev] is_a(), PEAR_Error and error mesages (newbie)

[Dmitry Diskin]

Hello,

I'm trying to modify ldap auth driver to make it possible to delete 
users from LDAP database. First of all, I set 'remove' capability to 
'true' in horde/lib/Auth/ldap.php. Next, I created function removeUser:

     function removeUser($userID)
     {
         $ldap = @ldap_connect($this->_params['hostspec']);

         $binddn = $this->_params['uid'] . '=' . 
$this->_params['username'] . ',' . $this->_params['basedn'];
         $bind = @ldap_bind($ldap, $binddn, $this->_params['password']);

         $dn = $this->_params['uid'] . '=' . $userID . ',' . 
$this->_params['basedn'];

         if (@ldap_delete($ldap, $dn)) {
             return AUTH_OK;
         } else {
             Horde::logMessage('removeUser: ' . @ldap_error($ldap), 
__FILE__, __LINE__, LOG_DEBUG);
             $this->_setAuthError(_("Remove failed."));
             return false;
         }
     }

And I'm keeping to receive "Successfully removed 'xxx' from the 
system.", while actually remove does not work and in horde.log I can see 
  this:

May 18 20:26:57 HORDE [debug] [horde] removeUser: Insufficient access 
[on line 176 of "/home/dda/horde/lib/Auth/ldap.php"]

According to the following code in horde/admin/user.php:

         if (is_a($auth->removeUser($f_user_name), 'PEAR_Error')) {
             $notification->push(sprintf(_("There was a problem removing 
'%s' from the system."), $f_user_name), 'horde.error');
         } else {
             $notification->push(sprintf(_("Successfully removed '%s' 
from the system."), $f_user_name), 'horde.success');
         }

I should receive '..was a problem..' message if removeUser() returns 
value of 'PEAR_Error' class. I used as an example function 
_authenticate($userID, $credentials) - comments to this function say: 
"@return boolean  True on success or a PEAR_Error object on failure." 
Please explain the following piece of code:

         $ldap = @ldap_connect($this->_params['hostspec']);
         if (!$ldap) {
             $this->_setAuthError(_("Failed to connect to LDAP server."));
             return false;
         }


I'm new to PHP, and I can't understand, first of all, how "return 
false;" can represent a PEAR_Error object.

Thank you for your help.
Dmitry.