White screen and unable to log php/smarty errors

[Hasher]

I have in php.ini:

display_errors = On

in config/defines.inc.php:

define('_PS_MODE_DEV_', true);

 

in smartyadmin.config.inc.php:

$smarty->debugging = true;

 

Some errors are logged into my php_error_log but not the one that is causing the white screen.

 

I am developing my own module and because of white screen I am unable to localise the error.

 

EDIT: I have found the reason of white screen - in AdminDeliverySlipController.php I had

Tools::redirectAdmin($this->context->link->getAdminLink('AdminPdf').'&submitAction=generateDeliverySlipsLabel&id_order='.Tools::getValue('id_order'));

instead of 

Tools::redirectAdmin($this->context->link->getAdminLink('AdminPdf').'&submitAction=generateDeliverySlipsPDFLabel&id_order='.Tools::getValue('id_order'));

 

but I would still like to know how to log such errors?

 

Edited August 5, 2015 by Hasher (see edit history)