Multiple submit buttons

Question

I have a registration form with two submit buttons. One submit button is for a free member account, and the other is for a premium member account.

My form code is

<form action="post.php" method="post">
<input type="text" name="name" />
<input type="text" name="mail" />

//submit buttons
<input type="submit" value="signup for free member" />
<input type="submit" value="signup for premium member" />
</form>

if($_POST['name'] and $_POST['mail']){
    $user_name = $_POST['name'];
    $mail = $_POST['mail']
    //How i can know he is preimum or free ?
    }

Now how can I tell whether the user clicked on the free button or the premium button?

example:

if($_POST['free_member']){
  $member = 'free';
}else{
  $member = 'premium';
}

Answer 1

HTML

<input type="submit" value="signup for free member" name="signup_free"/>
<input type="submit" value="signup for premium member" name="signup_premium"/>

PHP

if($_POST['signup_free'])
{
    $member = 'free';
}
elseif($_POST['signup_premium'])
{
    $member = 'premium';
}