combining error and processing output into the same form file?

I found the following script below that works well, but I would like to condense it down into one file.
http://www.plus2net.com/php_tutorial/tell_friend.php

It is a pretty simple script which consists of Tell.php and tellchk.php (Tell.php contains the form and tellchk.php processes data and sends the referral).  The issue I have is that I am using an include statement to include Tell.php into a site and tellchk.php doesn't fit the look of the site. 

I have used 2 files such as this in many other things, but for this it should work better combining everything together.  I have seen <?php echo $_SERVER['PHP_SELF']; ?> used when doing this, but I am not sure about the syntax to be able to include the validation and mail processing into just Tell.php  If someone could take a look at it I would appreciate it.  BTW I am using this in a shopping cart to send the referral link of that particular item. 

Thank you

Form and processing in one script can be done like this:

Code:

<?php
if($_POST['name']){
//error checking

//processing

}
else  {
//show form
?>
<form action="<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
</form>
<?php } ?>

Thank you Mind_nl.  Using your example I was able to get this to work.  The person I am helping on this decided to go with the 2 page setup after all, so I had to change the code on the second file to fit the site.  Thank you for your example, now I can use this in the future.

[Guest]

[62.885]

Googlebot