Need some more help, few PHP things.

<?php include("conf.php"); ?>

<?php
$act = $_GET['act'];
if ($act == "dosignup")
{
	sign_up($_POST['username'], $_REQUEST['password1'], $_REQUEST['password2'], $_REQUEST['email'], $_REQUEST['firstname'], $_REQUEST['lastname']);
}

function sign_up($username, $password1, $password2, $email, $firstname, $lastname)
{
	$md5_pass = md5($password1);

	if (! $password1 || ! $password2 || ! $email  || ! $username)
	{
		$error = "Must enter username and password and email.";
	}
	else if( $password1 != $password2 )
	{
		$error = "Your passwords do not match.";
	}
	else if (strlen($username) < 6)
	{
		$error = "Username must be over 6 characters";
	} else if (eregi('[!@#$%^&*()<>]', $username))
	{
		$error = "Invalid Characters in the username field";
	}
	else if (eregi('[!@#$%^&*()<>]', $password1) || eregi('[!@#$%^&*()<>]', $password2))
	{
		$error = "Invalid Characters in the password field";
	}
	else if (eregi('[!#$%^&*()<>]', $email))
	{
		$error = "Invalid Characters in the email field";
	}
	else if (eregi('[!@#$%^&*()<>]', $firtsname))
	{
		$error = "Invalid Characters in the first name.";
	} else if (eregi('[!@#$%^&*()<>]', $lastsname))
	{
		$error = "Invalid Characters in the last name.";
	}
	if (! $error)
	{

		$numRows = mysql_num_rows(mysql_query("SELECT * FROM `users` WHERE `username`='$username'"));
		if ($numRows > 0)
		{

			$error = "That account already exists.";
		}

		if (! $error)
		{
			$insert_query = mysql_query("INSERT INTO `users`(username, password, email, registration_date) VALUES('$username', '$md5_pass', '$email', CURRENT_DATE())") or die(mysql_error());
			if (! $insert_query)
			{
				$error = "Could not create account.";
			} else {
				main_view('Signup Form', 'Congratulations. Your account '.$username.' has been created. Please login to the left.');
				exit;
			}
		}
	}
	if ($error) { main_view('Login Error', "<b><font face='verdana' size='2'>Error: </b>".$error); exit; }
}

if ($act != "dosignup")
{
	?>	<h2><?php echo $website_name; ?> - Register</h2><br />
			<p> Please ensure that the below information is correct, otherwise you may not be able to retreive and use your account at a later stage.</font><br /><br />
			<form action='signup.php?act=dosignup' method='post'>
				<table width='100%' cellpadding='2' border='0'><tr><td bgcolor='#F0FFFF' width='100%'><font size='2' face='sans-serif'>Account Information</font></td></tr></table>
				<table width='400' border='0'>
					<tr>
						<td with='35%'><font size='2' face='sans-serif'>Desired Username:</font></td>
						<td width='65%'><input type='text' name='username' size='20'></td>
					</tr>
					<tr>
						<td width='35%'><font size='2' face='sans-serif'>Desired Password:</font></td>
						<td width='65%'><input type='password' name='password1' size='20'></td>
					</tr>
					<tr>
						<td width='35%'><font size='2' face='sans-serif'>Password (Again):</font></td>
						<td width='65%'><input type='password' name='password2' size='20'></td>
					</tr>
					<tr>
						<td width='35%'><font size='2' face='sans-serif'>Email:</font></td>
						<td width='65%'><input type='text' name='email' size='20'>
					</tr>
				</table>
				<br />
				<center><input type='submit' value='Create Account'></center>
							
			</form>
			</p>
			</div>
<?php
}
?>

<?php include_once("functions/footer.php"); ?>

	else if (strlen($username) < 6)

<?php

$special_request=true;
inclide('confi.php");
check_login($_REQUEST['username'], $_POST['password']);

?>

function check_login {

if (strlen($username) < 6)