Need help with a variable in a form

[freshfitz]

I need to add a variable to a pre made form this site uses smarty theme templates. I added an extra field member_id how do I get $post_data['member_id'] to show up in the body of the email?
I would think I would want ->setContent($post_data['message']['member_id']); but that does not work
I can change ->setContent($post_data['message']; to ->setContent($post_data['member_id']; and it will post the member_id

$toEmail = $email_arr[$post_data['feedback_to']];
		
		try {
			$msg = app_Mail::createMessage(app_Mail::FAST_MESSAGE)
					->setRecipientEmail($toEmail)
					->setSenderEmail((@$profile_fields['email']) ? $profile_fields['email'] : trim( $post_data['member_email'] ))
					->setSenderName((@$profile_fields['username']) ? $profile_fields['username'] : trim( $post_data['member_email'] ))
					->setSubject($post_data['subject'])
					->setContent($post_data['message']);
					
			app_Mail::send($msg);
		} catch (SK_EmailException $e) {
			if ($e->getCode() == SK_EmailException::WRONG_SENDER_EMAIL_ADDR)
			{
				$response->addError($lang_errors->text('false_email'), "member_email");
				return;
			}
		}
				
		$_SESSION['feedback_to'] = $post_data['feedback_to'];
		$response->redirect( SK_Navigation::href('contact') );
	}
}