PHP produces a completely white page, no errors, logs, or headers.

You could have a .htaccess file in this directory which has modified error reporting.

To test, try explicitly setting these options at the top of your php script which is giving you trouble.

ini_set('display_errors',1);
error_reporting(E_ALL);

I've also seen this caused by over-zealous anti-virus packages. Some contain web proxy software to filter internet and email. In that case, the page would just continue load into infinity but never complete.

Run the page from a console and you'll get the error message.

// nix
php yourFile.php

// Windows
c:\path\to\php.exe yourFile.php