<?php
$username = $_POST['username'];
$password = $_POST['password'];
$password2 = $_POST['password2'];
$email = $_POST['email'];
$errors = array();

$pattern = "/^([a-zA-Z0-9])+([\.a-zA-Z0-9_-])*@([a-zA-Z0-9_-])+(\.[a-zA-Z0-9_-]+)+/";
if(!empty($_POST))
{
    if($password != $password2)
    {
        $errors[] = 'Passwords do not match, please check the passwords you filled in.';
    }
    if(strlen($username) < 1)
    {
        $errors[] = 'Username too short, at least 1 character';
    }
    if(strlen($password) < 4)
    {
        $errors[] = 'Password too short, at least 4 characters';
    }
    if(!preg_match("/^([a-zA-Z0-9])+([a-zA-Z0-9\._-])*@([a-zA-Z0-9_-])+([a-zA-Z0-9\._-]+)+$/", $email))
    {
        $errors[] = 'E-mail isn\'t valid, please check the e-mail you filled in.';
    }
    if(!empty($errors))
    {
        echo '<fieldset id="error">';
        echo '<legend>Error\'s</legend>';
        foreach ($errors as $error)
        {
            echo '<span class="error">'.$error.'</span><br />';
        }
        echo '</fieldset>';
    } else {
        echo 'Hallon';
    }
}
?>
<form action="?page=register" method="post">
<fieldset>
    <legend>User information</legend>

    <span>Username:</span><input type="text" name="username">
    <br />
    <span>Password:</span><input type="password" name="password">
    <br />
    <span>Verify Password:</span><input type="password" name="password2">
    <br />
    <span>E-Mail:</span><input type="text" name="email">
    <br />
    <input type="submit" value="Register">

</fieldset>
</form>