<?php

// $_POST['submit'] NOT SET
if (!isset($_POST['submit'])) { ?>

	<form action="page.php" method="POST" >
		<span>Username: </span><input type="text" name="username" />
		<span>Password: </span><input type="text" name="password" />
		<span>Repeat ^: </span><input type="password" name="check_password" />
		<span>Email Address: </span><input type="email" name="email" />
	</form>

<?php }

// $_POST['submit'] SET
if (isset($_POST['submit'])) {

	// define variables
	$username = $_POST['username'];
	$password = $_POST['password'];
	$check_password = $_POST['check_password'];
	$email = $_POST['email'];

	// check for empty variables, echo, then die if true.
	if (empty($username)) {
		echo "Username Blank!";
	}
		elseif (empty($password)) {
			echo "Password Blank!";
		}
			elseif (empty($check_password)) {
				echo "Check Password Blank!";
			}
		elseif (empty($email) {
			echo "Email Blank!";
		}
	if (empty($username) || empty($password) || empty($check_password) || empty($email)) {
		exit();
	}

		// $password does not equal $check_password
		if ($password!=$check_password) {
			die("Passwords do NOT match!");
		}

	// Echo Variables
	echo "Welcome" . " " . $username . "<br />";
	echo "Your Password" . ": " . $password . "<br />";
	echo "Your Email" . ": " . $email . "<br />";

	// Send user an email with PHP Mail.
	$to = 'test@example.com';
	$subject = 'TEST';
	$message = 'Test Email upon Registration.';
	$headers = 'From: from@example.com' . "\r\n" .
   		'Reply-To: from@example.com' . "\r\n" .
    		'X-Mailer: PHP/' . phpversion();
	mail($to, $subject, $message, $headers);
}
?>