php radio button email - php

Question

I am trying to make a form to ask people if they are attending an event. I have searched multiple threads and forums. I also resorted to google and read through a few tutorials and I am unable to correlate the correct answers to what I need. I am trying to figure out how to send an e-mail to with a message based on the radio button selected. Please help me if you can. It is greatly appreciated.
<FORM method="post" name="RSVPform" action="respond.php" target="_blank">
Name(s): <input name="name" size="42" type="text" /><br/><br/>
Will you be attending the event?<br/><br/>
<input checked="checked" name="answer" type="radio" value="true" /> Yes, I(we) will attend.<br/><br/>
If yes, how many will be attending? <input name="number" size="25" type="text" /><br/><br/>
<input name="answer" type="radio" value="false"/>Sadly, we are unable to attend. <br/><br/> <input name="Submit" type="submit" value="Submit" />
</FORM>
This is the php I've been trying to use.
<?php
$to = "myemail#email.com";
$name = $_REQUEST['name'] ;
$answer = $_REQUEST['answer'] ;
$subject = "RSVP from: $name";
$number = $_REQUEST['number'] ;
$headers = "RSVP";
$body = "From: $name, \n\n I(we) will be attending the event. There will be $number of us. \n\n Thanks for the invite.";
$sent = mail($to, $subject, $body, $headers) ;
if($sent)
{echo "<script language=javascript>window.location = 'LINK BACK TO CONTACT PAGE';</script>";}
else
{echo "<script language=javascript>window.location = 'LINK BACK TO CONTACT PAGE';</script>";}
?>
I'm not sure how to change the $body message depending on the radio button selected. Is this possible?

Answer 1

You need a condition in the PHP, but note that in your HTML "true" and "false" will be sent as strings not booleans, so are both truthy, but you can check the actual string.
Anywhere after $answer = $_REQUEST['answer'] ; append/modify/write your email body, e.g.
if ($answer=='true') {
$body='Yay you\'re coming';
}else{
$body='Ah screw you then';
}

Answer 2

Here's the absolute basic of what you'd need. Just swap your variables based on the posted answer.
if($_POST['answer'] == "true")
{
// user is coming
}
else
{
// user is not coming
}