Question

I have a database that stores image urls andother data, I want a gallery to display them but because the site is public I may want to delete some images. When a user uploads an image source and title, it is inserted into the database with an auto increment unique ID. The current script only adds or subtracts 1 from the ID to display the next or previous image. Is there any better way of doing this?
My current script:

function image_control($id){
$next=$id+'1';
$prev=$id-'1';
$query = "SELECT MAX(id), MIN(id) FROM mp_images";
$result = mysql_query($query) or die(mysql_error());
while($row = mysql_fetch_array($result)){
    $max = $row['MAX(id)']; $min = $row['MIN(id)'];
}
if($next==$max+"1"){$next=$min;} if($prev==$min-"1"){$prev=$max;}
echo "<a href='".$next."'>Next Image</a> <a href='".$prev."'>Previous Image</a>";
}

An example of this failing would be images where the ID’s are 3,4,5,7,8.

Answer 1

some pseudo code for getting the next id:

$nextId = SELECT id FROM mp_images WHERE id > $currentId ORDER BY id ASC LIMIT 1
if ( no results )
  // no next image

and for the previous:

$prevId = SELECT id FROM mp_images WHERE id < $currentId ORDER BY id DESC LIMIT 1
if ( no results )
  // no previous image

It’s up to you on what to do if there is no next image (you could for instance fetch the first image) or no previous image (you are on the first image).