Inkblot authentication

<?php

session_start();
include("./inkblot_auth.php");
//provide path to directory with inkblot images
$ink = new inkblot_auth("./inkblots");

if(isset($_SESSION["pass"]))
{
    //we already created pass for testing
    echo "<h3>You have successfully registered. Now try to login using same password</h3>";
    
    //first we need to provide password which we previously saved
    //usually it is retrieved form database using provided username
    //but for testing we've saved in in session variable
    $ink->set_pass($_SESSION["pass"]);
    
    if(isset($_POST["logpass"]))
    {
        //no we check user provided password
        //only after providing saved password
        if($ink->check_pass($_POST["logpass"]))
        {
            echo "<h3>You provided correct password</h3>";
        }
        else
        {
            echo "<h3>Your password is incorrect</h3>";
        }
    }
    
    //now we will get inkblots that were used in pasword
    $inks = $ink->get_inkblots();
    echo "<div style='overflow: auto; margin-bottom: 50px;'>";
    foreach($inks as $val)
    {
        echo "<img src='".$val."' 
            style='float: left; margin-right: 10px; width: 200px;'/>";
    }
    echo "</div>";
    echo "<p>All you have to do is remember your password while seeing same 
    inkblots, that you saw when you created this password.</p>
    <p>Just insert your first and last letter of your inkblot interpretations 
        in inkblot order (from left to right)</p>";
    echo "<form action='' method='post'>
    <p>Enter your saved password: <input type='text' name='logpass'/> 
    <input type='submit' value='Register'/></p>
    </form>";
}
else
{
    //someone submitted pass
    if(isset($_POST["regpass"]))
    {
        //get encoded pass and save it
        $_SESSION["pass"] = $ink->get_pass($_POST["regpass"]);
        //refresh page
        header("Location: ".$_SERVER["REQUEST_URI"]);
    }
    echo "<h3>Create new password (Simulating registration)</h3>";
    //no pass created
    $inks = $ink->get_inkblots();
    echo "<div style='overflow: auto; margin-bottom: 50px;'>";
    foreach($inks as $val)
    {
        echo "<img src='".$val."' 
            style='float: left; margin-right: 10px; width: 200px;'/>";
    }
    echo "</div>";
    echo "<p>This login is based on user choosing and remembering the password 
        based on inkblot that user see.</p>
<p>Because human mind interprets each inkblot differently, it means, that it is 
    possible that no one else will see a thing that you saw.</p>
<p>You must type first and last letter of each inkblot interpretation based on 
sequence you see those inkblots (from left to right)</p>
<p>Then each time you'll try to login, you'll see same inkblot images only each 
time in different order</p>
<p>Refresh page to change inkblots</p>";
    echo "<form action='' method='post'>
    <p>Enter your password: <input type='text' name='regpass'/> 
    <input type='submit' value='Register'/></p>
    </form>";
}
?>