ActionScript 2.0 :: Email Capture Form - GetURL Not Sending Variable

I'm trying to make a small email capture form, but I'm having trouble getting Flash to pass the email address to the server. I've since given up trying to use getURL and I'm simply trying to trace the variable instead. The form consists of a text box w/ instance name "email_txt" and a button w/ instance name "btnSignUp." the actionscript is placed on the button.

Here's PHP Code:
on(release) {
trace("email_txt says: " + email_txt);
// getURL stuff here
}

My trace statement reads:
Code:
email_txt says: undefined