Error op aparte pagina

<?php
	require_once("error.inc.php");

        if(IsSet($_POST['register'])) {
        	$userName = stripslashes($_POST['username']);
		$firstName = stripslashes($_POST['first_name']);
		$lastName = stripslashes($_POST['last_name']);
		$mail = stripslashes($_POST['mail']);

		$error->emptyFields($userName, $firstName, $lastName, $mail);
	}
?>
	<form action="" method="POST">
		<table cellpadding="3" cellspacing="0" border="0">
		<tr>
        		<td>Username:</td>
        		<td><input type="tekst" name="username" maxlength="16" length="30" /></td>
        	</tr>
                <tr>
        		<td>Firstname:</td>
        		<td><input type="tekst" name="first_name" maxlength="25" length="30" /></td>
        	</tr>
                <tr>
        		<td>Surname:</td>
        		<td><input type="tekst" name="last_name" maxlength="25" length="30" /></td>
        	</tr>
                <tr>
        		<td>E-mail address:</td>
        		<td><input type="tekst" name="mail" maxlength="25" length="30" /></td>
        	</tr>
        	<tr>
        		<td colspan="2"><button type="submit" name="register">Register</button></td>
        	</tr>
        	</table>
	</form>

<?php
	require_once("error.inc.php");
 
        if(IsSet($_POST['register'])) {
        	$userName = stripslashes($_POST['username']);
		$firstName = stripslashes($_POST['first_name']);
		$lastName = stripslashes($_POST['last_name']);
		$mail = stripslashes($_POST['mail']);
 
		$error->emptyFields($userName, $firstName, $lastName, $mail);
	}
?>
	<form action="" method="POST">
		<table cellpadding="3" cellspacing="0" border="0">
		<tr>
        		<td>Username:</td>
        		<td><input type="tekst" name="username" maxlength="16" length="30" /></td>
        	</tr>
                <tr>
        		<td>Firstname:</td>
        		<td><input type="tekst" name="first_name" maxlength="25" length="30" /></td>
        	</tr>
                <tr>
        		<td>Surname:</td>
        		<td><input type="tekst" name="last_name" maxlength="25" length="30" /></td>
        	</tr>
                <tr>
        		<td>E-mail address:</td>
        		<td><input type="tekst" name="mail" maxlength="25" length="30" /></td>
        	</tr>
        	<tr>
        		<td colspan="2"><button type="submit" name="register">Register</button></td>
        	</tr>
        	</table>
	</form>

<?php
	class error_handling {

                function emptyFields($name, $last, $first, $mail) {
                	if(empty($name) || empty($last) || empty($first) || empty($mail)) {
                        	print("You haven't filled in all information:");
                                if(empty($name)) {
                                	print("<br />- Username is empty");
                                }
                                if(empty($last)) {
                                	print("<br />- Surname is empty");
                                }
                                if(empty($first)) {
                                	print("<br />- Firstname is empty");
                                }
                                if(empty($mail)) {
                                	print("<br />- E-Mail address is empty");
                                }
                	}
                }

	}

	$error = new error_handling;
?>

<?php
	class error_handling {
 
                function emptyFields($name, $last, $first, $mail) {
                	if(empty($name) || empty($last) || empty($first) || empty($mail)) {
                        	print("You haven't filled in all information:");
                                if(empty($name)) {
                                	print("<br />- Username is empty");
                                }
                                if(empty($last)) {
                                	print("<br />- Surname is empty");
                                }
                                if(empty($first)) {
                                	print("<br />- Firstname is empty");
                                }
                                if(empty($mail)) {
                                	print("<br />- E-Mail address is empty");
                                }
                	}
                }
 
	}
 
	$error = new error_handling;
?>