Help with attach file

Is it possible to attach a text file that includes the content of a form
name/variable?

This is what I have tried so far without success:


function test_Plain_StringAttachment() {

$this->Mail->Body = "Hello. Body here. ";
$this->Mail->Subject .= " Subject here";

$this->Mail->AddStringAttachment($comments, "filename.txt");

$this->assert($this->Mail->Send(), $this->Mail->ErrorInfo);
}



All I get is the text file titled "filename.txt" but an empty file.

However, when I change the code to read:

$comment = "Hi and welcome to the text file.";

$this->Mail->AddStringAttachment($comment, "filename.txt");

The file includes the text "Hi and welcome to the text file." as it should.

Has anyone had any success, is it possible to do this?

Thank you.

helen