Help please! – Loop work fine on local server but doesn't so on website

I have edited the loop to display a link to the file attached inside a post in the “post meta data” area. While I am running the loop on my localserver installation, everything works just fine, I get everything displayed correctly, something like this

Post 1
link | comments etc…

Post 2
link | comments etc…

But on the website it doesn’t work! (While displaying posts on the search result page, the link reffers to the search link)
For example, searching for post Title1, I get this

Search results

Title1
link | comments etc…
but the link doesn’t refer to the attachment inside the post, but to the current url (websiteurl/?s=Title1&submit=Go)

I am using the same theme, with the same files. So I don’t understand why it isn’t working on the website, but it does so on the localhost.

Here is the code I used inside the loop to get the attachment url:

$docs =& get_children( array('post_parent' => $post->ID, 'post_type' => 'attachment', 'post_mime_type' => 'application/pdf', 'order' => 'ASC', 'orderby' => 'menu_order ID') );

if ( empty($docs) ) {
	$attachment_url = "#";
} else {
	foreach ( $docs as $attachment_id => $attachment ) {
		$attachment_url =& wp_get_attachment_url( $attachment_id );
	}
}
?>

And then somewhere below, this, to display the link where I want it:
<a href="<?php echo $attachment_url ?>"> Download </a> | <a href="localhost/"

Again, I am using exactly the same theme with the same files.
What is wrong?
Please help me.
Best regards,
Radu