Before this I was able to get image URL for background-image in page list using

$img->getTag()->src; //this gives me the thumbnail url

However, now I want to use the responsive feature for thumbnail, so I did this in page_theme.php

public function getThemeResponsiveImageMap()
{
return array(
'small' => '0'
);
}

$img->getTag()->src; //this doesn't work anymore even if i did, i won't get the 'small' version of the thumbnail.

For those who know, please tell me how to get the src for thumbnail if responsive feature is enabled.

<?php
$img = Core::make('html/image', array($thumbnail));
$tag = $img->getTag();
$tag->addClass('img-responsive');
print $tag;
?> //this works but I just need the URL instead of the whole <img></img>