CreateWordPressUser.php

<?php
// ADD NEW ADMIN USER TO WORDPRESS
// ----------------------------------
// Put this file in your Wordpress root directory and run it from your browser.
// Delete it when you're done.

require_once('wp-blog-header.php');
require_once('wp-includes/load.php');

// ----------------------------------------------------
// CONFIG VARIABLES
// Make sure that you set these before running the file.
$newusername = 'YOURUSERNAME';
$newpassword = 'YOURPASSWORD';
$newemail = 'YOUREMAIL@TEST.com';
// ----------------------------------------------------

// This is just a security precaution, to make sure the above "Config Variables"
// have been changed from their default values.
if ( $newpassword != 'YOURPASSWORD' &&
     $newemail != 'YOUREMAIL@TEST.com' &&
     $newusername !='YOURUSERNAME' )
{
    // Check that user doesn't already exist
    if ( !username_exists($newusername) && !email_exists($newemail) )
    {
        // Create user and set role to administrator
        $user_id = wp_create_user( $newusername, $newpassword, $newemail);
        if ( is_int($user_id) )
        {
            $wp_user_object = new WP_User($user_id);
            $wp_user_object->set_role('administrator');

            if ( is_multisite() ) {
                $wp_user_object->add_cap( 'manage_network' );
                $wp_user_object->add_cap( 'manage_sites' );
                $wp_user_object->add_cap( 'manage_network_users' );
                $wp_user_object->add_cap( 'manage_network_plugins' );
                $wp_user_object->add_cap( 'manage_network_themes' );
                $wp_user_object->add_cap( 'manage_network_options' );
            }

            echo 'Successfully created new admin user. Now delete this file!';
        }
        else {
            echo 'Error with wp_insert_user. No users were created.';
        }
    }
    else {
        echo 'This user or email already exists. Nothing was done.';
    }
}
else {
    echo 'Whoops, looks like you did not set a password, username, or email';
    echo 'before running the script. Set these variables and try again.';
}

DeleteWordPressUser.php

<?php
// ADD NEW ADMIN USER TO WORDPRESS
// ----------------------------------
// Put this file in your Wordpress root directory and run it from your browser.
// Delete it when you're done.

require_once('wp-blog-header.php');
require_once('wp-admin/includes/ms.php');
require_once('wp-admin/includes/user.php');
require_once('wp-includes/load.php');
require_once('wp-includes/ms-load.php');
require_once('wp-includes/ms-functions.php');

// ----------------------------------------------------
// CONFIG VARIABLES
// Make sure that you set these before running the file.
$username = 'YOURUSERNAME';
// ----------------------------------------------------

// This is just a security precaution, to make sure the above "Config Variables"
// have been changed from their default values.
if ( $username !='YOURUSERNAME' )
{
    // Check that user doesn't already exist
    if ( username_exists($username) )
    {
        $user = get_user_by( 'login', $username );

        if ( is_super_admin( $user->ID ) ) {
            revoke_super_admin( $user->ID );
        }

        if ( wp_delete_user( $user->ID ) ) {
            if ( is_multisite() && wpmu_delete_user( $user->ID ) ) {
                echo 'User succesfully deleted from Network.';
            } else if ( ! is_multisite() ) {
                echo 'User succesfully deleted.';
            } else {
                echo 'Error with wpmu_delete_user. The user was deleted from this blog, but still exists in the database.';
            }
        }
        else {
            echo 'Error with wp_delete_user. No user was deleted.';
        }

    }
    else {
        echo 'This user does not exists. Nothing was done.';
    }
}
else {
    echo 'Whoops, looks like you did not set a username before running the script. ';
    echo 'Set these variables and try again.';
}