always-login.php

<?php

/**
 * keeps a user always logged in
 * don't use this on a production site, ever!
 */

add_action( 'init', 'rkv_auto_login' );
add_action( 'admin_init', 'rkv_auto_login' );

function rkv_auto_login() {
	
	// bail on ajax
	if ( defined( 'DOING_AJAX' ) && DOING_AJAX ) {
		return;
	}

	// bail if the user is logged in
	if ( is_user_logged_in() ) {
		return;
	}

	// get the user
	$user   = get_userdata( 1 ); // 1 being the ID that I want

	// bail if I don't have userdata
	if ( empty( $user ) || ! is_object( $user ) ) {
		return;
	}

	// set the current user
	wp_set_current_user( $user->ID, $user->user_login );
	
	// set the auth cookie
	wp_set_auth_cookie( $user->ID );
	
	// now actually log in
	do_action( 'wp_login', $user->user_login );	
}