Magento How to debug blank white screen

Question

I have an error in my Magento backend that results in a blank screen (WSOD). I have set errors to on in admin but there is nothing being created in var/logs/. (I have checke

Answer 1

This is how I got it corrected(Hope will help you guys):

1. Use the following code in your index.php file

   ini_set('error_reporting', E_ERROR);
   register_shutdown_function("fatal_handler");
   function fatal_handler() {
       $error = error_get_last();
       echo("<pre>");
       print_r($error);
   }
   

2. In my case it tolde me that error/503.php was unavailable.

3.The issue was with testimonial extension I used(http://www.magentocommerce.com/magento-connect/magebuzz-free-testimonial.html)

4. I deleted the testimonial.xml file in my app/etc/modules/testimoanial.xml.
5. delete “maintenance.flag" file.

Answer 2

ANOTHER REASON

for a white screen without error messages might be fragmentation of the APC cache.

Use phpinfo() to find out if it is used by your page (we had issues with PHP 5.4 + APC 3.1.13) and if so see what happens when you either

• disable it via .htaccess: php_flag apc.cache_by_default off
• clear the apc cache every time the page is called: add at the top of index.php apc_clear_cache(); (no solution but good to see if the APC is the problem)

If you do have the APC and it is the problem, then you could

• play around with its settings, which might be cumbersome and still not work at all
• just update to PHP 5.5 and use its integrated opcode cache instead.

Answer 3

In my case size of the index.php file was zero. I copied the original file back and it worked.

However, no idea about what erased the content of index.php.

Answer 4

Following can be the reasons for the blank pages in magento

1) File or Directory permission issues. If you are migrating from one server to another remember to give 755 permission to the directories and files

2) If you were working on an xml file and suddenly the pages go blank. Check you might not have commented the code lines properly.An unclosed comment will also create the problem.

3) There may be issue because of insufficient memory allocation for memory_limit.

4) Try clearing the var/cache folder contents

5) Try clearing the var/session folder contents

6) If your extensions use ioncube loader on production then install ion cube on development server also.(Like for extendware extensions).Though you may have ion cube loader try installing the latest version.Because some time when you update the extensions which depends on ion cube there is incompatibility with older versions.

7) Set short_open_tag = On in php.ini .Some times developers use <? ?> tags and if the short_open_tag is not set to on you may face problems like half distorted page etc.

8) Increase max_input_vars and post_max_size values for php. It helps when you try to save large number of tax rates in a tax rule and get a blank page.

Answer 5

My solution: Activating the plugin via System -> Config > Advanced > Advanced

Answer 6

As you said - there is one stand alone answer to this issue.

I had same issue after changing theme. Memory was set to 1024 before, so that's not the problem. Cache was cleared and there was nothing useful in error log.

In my case solution was different - old theme had custom homepage template... Switching it to standard one fixed it.