Echo other content after form validation and submission - php

Question

How to clear page content and show other content after I validate and submit a form?
<?php
if(isset($_POST['Confirm'])) {
$to = "email#email.com";
$error = 0;
$first_name = $_POST['first_name'];
//Validation things
if(trim($first_name) == '') {$error = 1; $first_namerr = 1;}
$msg ="
First Name:$first_name
-------------------------
";
$sub ="Contact";
$from = "From: Support form";
#mail($to, $sub, $msg, $from);
//How to clear actual content and echo other ?
}
}
?>
<form name="contact" id="contact" method="post" action="<? echo $_SERVER['PHP_SELF']; ?>">
<label for="first_name" class="inner_text"><?php if ($error != 0){ if ($first_namerr == 1) {print("<font style='color: Red;'>");} }?>First Name<?php if ($error != 0){if ($first_namerr == 1) {print("</font>");}} ?></label>
<input id="first_name" name="first_name" size="30" type="text" value="<? echo $first_name; ?>" /><?php if ($error != 0){ if ($first_namerr == 1) {print('<img src="images/error.gif">');} }?>
<input type="submit" id="Confirm" name="Confirm" value="Confirm" />
</form>
I'm beginner in PHP, so please be explicit if you want to give an answer!

Answer 1

You could use an if/else statement to control the content being displayed - e.g:
<?php
if (isset($_POST['Confirm'])) {
// Your mail code
?>
Thank you, your message has been sent! <!-- This content is shown after form submission -->
<?php } else { ?>
<!-- Display your email form -->
<?php }; ?>