Use unique membership key as username with PMPro checkout

my_init_unique_key_as_username.php

<?php // Do not copy this tag

// Use unique membership key as username with PMPro checkout. You'll also have to hide the username fields at checkout using CSS or a custom checkout page template.
// Paste the code below into a PMPro Customization Plugin: https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/

function my_init_unique_key_as_username()
{
	$args = array(
		'role'         => 'author', // authors only
		'orderby'      => 'registered', // registered date
		'order'        => 'DESC', // last registered goes first
		'number'       => 1 // limit to the last one, not required
	);
	
	$users = get_users( $args );
	
	$last_user_registered = $users[0]; // the first user from the list
	$new_user_id = $last_user_registered->ID;

	$scramble = md5(AUTH_KEY . current_time('timestamp') . ( $new_user_id + 1 ) . SECURE_AUTH_KEY);
	$unique_member_key = substr($scramble, 0, 10);

  //check for level as well to make sure we're on checkout page
  if(empty($_REQUEST['level']))
    return;
  
  if(!empty($_REQUEST['bemail']))
    $_REQUEST['username'] = $unique_member_key;
    
  if(!empty($_POST['bemail']))
    $_POST['username'] = $unique_member_key;
    
  if(!empty($_GET['bemail']))
    $_GET['username'] = $unique_member_key;
}
add_action('init', 'my_init_unique_key_as_username');