在php中为css获取背景图像的正确方法是什么？

I have the following function that I'm trying to use to get an image in the same directory as the plugin but inside the images folder.

function my_login_logo() { ?>
<style type="text/css">
    #login h1 a, .login h1 a {
        background-image: url(<?php echo dirname(__FILE__); ?>/images/logo3.png);
    height:65px;
    width:320px;
    background-size: 320px 65px;
    background-repeat: no-repeat;
        padding-bottom: 30px;
    }
</style>

its is taken from the following, which works fine. yes "/" works.

function my_login_logo() { ?>
<style type="text/css">
    #login h1 a, .login h1 a {
        background-image: url(<?php echo get_stylesheet_directory_uri(); ?>/images/site-login-logo.png);
    height:65px;
    width:320px;
    background-size: 320px 65px;
    background-repeat: no-repeat;
        padding-bottom: 30px;
    }
</style>

What am I doing wrong?