PHP Form submit problems

I tried making a new page from the pages-default.php. I’m using the carrington theme. The code looks like this:

<?php

/*
Template Name: Boyfriendnicknames
*/

// This file is part of the Carrington Blog Theme for WordPress
// https://carringtontheme.com
//
// Copyright (c) 2008-2009 Crowd Favorite, Ltd. All rights reserved.
// https://crowdfavorite.com
//
// Released under the GPL license
// https://www.opensource.org/licenses/gpl-license.php
//
// **********************************************************************
// This program is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
// **********************************************************************

if (__FILE__ == $_SERVER['SCRIPT_FILENAME']) { die(); }
if (CFCT_DEBUG) { cfct_banner(__FILE__); }

get_header();

?>

<div id="content">
<h2>Generate Your Wu-Name</h2>
<p><hr size=1 noshade></p>

  <form action="<?php echo $_SERVER['PHP_SELF']; ?>" METHOD="POST">
    <p><b>Enter your Name: </b><br />
    <input type="text" name="realname" size=25> &nbsp; &nbsp;
    <input type="submit" value="Submit">
    </p>
  </form>

<p><hr size=1 noshade></p>

<?
if ($_SERVER['REQUEST_METHOD'] == "POST") {
    $realname = $_POST['realname'];
    $displayname = $realname;
    $realname = strtolower($realname);

    /*== generate seed number from name submitted ==*/
    $len = strlen($realname);
    $seed = 0; $s = 0;

    for ($e=1; $e<=$len; $e++)
    {
      $chr = substr($realname,$s,$e);
      $seed = $seed + ord($chr)*$e;

      $s=$e;
    }

    /*== read in the two files into the arrays ==*/
    $adj_array = file("wu_adjs.txt");
    $noun_array = file("wu_nouns.txt");

    /*== set random seed ==*/
    srand($seed);

    /*== get the random numbers for each name first/last or adj/noun ==*/
    $arnd = rand(0,sizeof($adj_array)-1);
    $nrnd = rand(0,sizeof($noun_array)-1);

    /*== create name from random numbers ==*/
    $wuname = "$adj_array[$arnd] $noun_array[$nrnd]";

    print "<p><font size=4><b>$displayname</b> from this day forward you <br />you will also be known as ";
    print "<font size='+1'><b> $wuname </b></font></font></p>";

  }

?>
    <div id="comments">
<?php
    comments_template();
?>
    </div><!--#comments-->
</div><!--#content-->

<?php

get_sidebar();
get_footer();

?>

But I am having the same problem. When I click submit, it returns me to the front page of my blog. I suspect that it has something to do with this line:

<form action="<?php echo $_SERVER['PHP_SELF']; ?>" METHOD="POST">

But I’m unsure how to fix it. Any help would be grateful.

You can test it here:
https://www.artifacting.com/blog/get-cute-nicknames-for-your-boyfriend-or-girlfriend/