PHPExcel_Writer_Exception with message "Could not close zip file php://output."

Thanks to Mark Baker. His answer has solved the problem. I have written a simple helper method using his approach.

static function SaveViaTempFile($objWriter){
    $filePath = sys_get_temp_dir() . "/" . rand(0, getrandmax()) . rand(0, getrandmax()) . ".tmp";
    $objWriter->save($filePath);
    readfile($filePath);
    unlink($filePath);
}

And I have just replaced $objWriter->save('php://output') with SaveViaTempFile($objWriter)

The most common cause of this error when saving to php://output is an open_basedir restriction that doesn't include a valid system's temp folder (e.g. /tmp), or permissions for the system's temp folder... suhosin can also affect this, even when the obvious permissions appear to be set correctly.

A possible workround is to write the file to the filesystem in a directory that you know you do have full privileges to write, and then use readfile() to stream that file to php://output before deleting the file