WordPress auto-login

developer_login.php

<?php
/*
 * Auto-login script to save having to manually login when developing a WP site.
 *
 * Place in wp-content/mu-plugins and remember to add to .gitignore for safety
 *
 * Add the DEV_GET_PARAMETER to the url to activate the script and login for you
 * e.g. http://localhost:8080/?dev
 */
 
define('DEV_HOST', 'localhost');
define('DEV_USER', 'admin');
define('DEV_GET_PARAMETER', 'dev');
 
add_action('plugins_loaded', 'developer_admin_login');

function developer_admin_login() {
	if ($_SERVER['SERVER_NAME'] === DEV_HOST && isset($_GET[DEV_GET_PARAMETER])) {
		$admin = get_user_by('login', DEV_USER);
		
		if ($admin && !is_user_logged_in()) {
			wp_set_auth_cookie($admin->ID);
		}
	}
}