first image from the wordpress post and display it, not working

i am using

function get_first_image() {
global $post, $posts;
$first_img = '';
ob_start();
ob_end_clean();
$output = preg_match_all('/<img.+src=[\'"]([^\'"]+)[\'"].*>/i', $post->post_content, $matches);
$first_img = $matches [1] [0];
if(empty($first_img)){ //Defines a default image
$first_img = "/images/default.jpg";
}
return $first_img;
}

Code (markup):

with

<?php echo get_first_image() ?>

Code (markup):

but on my home page, its just showing the image link

can any one help out?
thanks.

 

use $matches[0][0] not [1][0]

if in doubt use print_r($matches); to see what is stored in the array.