Use CURL to get filesize on 32bit systems.
Cast to numeric instead of float, i.e. use an integer if possible.
Refactor Large File handling code.
Unit Tests for LargeFileHelper.
Output validation for exec() method.
Windows exec() implementation.
Only call $this->filesize() for files.
Rename: LargeFileHelper -> LargeFileHelperGetFilesize
Add helper method for turning int|float into base-10 unsigned integer string.
Add LargeFileHelper::__construct() verifying that our assumptions hold.