Compare two files based on size and file name.
protected function drupalCompareFiles($file1, $file2) {
$compare_size = filesize($file1->uri) - filesize($file2->uri);
if ($compare_size) {
// Sort by file size.
return $compare_size;
}
else {
// The files were the same size, so sort alphabetically.
return strnatcmp($file1->name, $file2->name);
}
}