Create WordPress Admin User from PHP

wp-new-user.php

<?php
/**
 * ADD NEW ADMIN USER TO WORDPRESS
 *
 * Put this file in your WordPress root directory and run it from your browser.
 * Add wp-new-user.php after your domain url.
 * Delete it when you're done.
 *
 * @link https://gist.github.com/overclokk/e63c15eb274532b68502685dc2952d26
 * @since 1.0.0
 *
 * @requirement WP >= 3.1
 */

require_once( 'wp-blog-header.php' );

/**
 * CONFIG VARIABLES
 * Make sure that you set these before running the file.
 */
$newusername = ''; // <- Enter the user name.
$newpassword = ''; // <- Enter the user password.
$newemail = ''; // <- Enter the user email.
$role = 'administrator'; // <- Enter the user role. Default 'administrator'

//----------------------------------------------------------//

if ( empty( $newusername ) ) {
	echo 'Whoops, looks like you did not set a username<br>';
	return;
}

if ( empty( $newpassword ) ) {
	echo 'Whoops, looks like you did not set a password<br>';
	return;
}

if ( empty( $newemail ) ) {
	echo 'Whoops, looks like you did not set an email<br>';
	return;
}

if ( false === is_email( $newemail ) ) {
	echo 'Whoops, looks like this is not a valid email<br>';
	return;
}

if ( ! in_array( $role, array( 'administrator', 'editor', 'author', 'contributor', 'subscriber' ) ) ) {
	echo 'Whoops, The user role is not set correctly.<br>';
	return;
}

if ( username_exists( $newusername ) ) {
	echo 'The user name already exists.<br>';
	return;
}

if ( email_exists( $newemail ) ) {
	echo 'The user email already exists.<br>';
	return;
}

/**
 * User ID|WP_Error
 *
 * @var int|WP_Error
 */
$user_id = wp_create_user( $newusername, $newpassword, $newemail );

if ( is_wp_error( $user_id ) || 0 === $user_id  ) {
	echo 'Error with wp_insert_user. No users were created.';
} else {
	$wp_user_object = new WP_User( absint( $user_id ) );
	$wp_user_object->set_role( $role );
	echo 'Successfully created new ' . $role . ' user. Now delete this file!';
}

return;