sprintf and php - sql

Question

The following function gives all the related data except artist_id, when run I have checked all elements in the database and ok.
If I change the artist_id to an actual 'id' it shows in the result of the function as WHERE artist_id = 4 AND........
Confess I do not understand what is causing this.
Result of the function:
SELECT `image_album_id`, `member_id`, `artist_id`, `albumname`, `ext`, `timestamp`
FROM album_images WHERE artist_id = AND member_id = 1 AND
image_album_id = 160
<?php
function get_data_nxtprv($fields, $where) {
$return = FALSE;
// Template
$template = "SELECT %s "
. "FROM album_images "
. "WHERE artist_id = " . $artist_id. "
AND member_id = ".$_SESSION['member_id']." %s";
// Current record
$sql = sprintf($template, $fields, $where);
$query = mysql_query($sql);
$query_result = mysql_fetch_assoc($query);
//print_r($sql);
// If data has been found
if ($query_result)
{
$return = $query_result;
}
return $return;
?>

Answer 1

I am not entirely sure I understand your question. But I noticed that your function uses three input variables:
$artist_id, $fields, $where
But $artist_id is not getting passed as an argument.
You would need to modify the function call:
function get_data_nxtprv($artist_id, $fields, $where)

Answer 2

There is an error in your SQL
SELECT `image_album_id`, `member_id`, `artist_id`, `albumname`, `ext`, `timestamp`
FROM album_images WHERE artist_id = AND member_id = 1 AND
image_album_id = 160
should it not be
SELECT `image_album_id`, `member_id`, `artist_id`, `albumname`, `ext`, `timestamp`
FROM album_images WHERE member_id = 1 AND
image_album_id = 160
if artist_id is one of the fields you're looking for?