During the Drupal development, sometimes you may find the white screen of death(WSOD) and you have no idea what’s happening. To tackle the WSOD, add the following lines in the index.php located in the Drupal webroot.

<?php

error_reporting(E_ALL);
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);

// $Id: index.php,v 1.94 2007/12/26...

The PHP error will be thrown instead of white screen. If this could not solve the problem, visit the following link and you should find more details about WSOD in Drupal.

Reference: The White Screen of Death (Completely Blank Page)