Array selecting

I'd like to query my database and ask it for an array of photo ids belonging to a user and order it by time desc. Then from that array i would like to select the photo one up or one down from the current photo. i was thinking i could then search the array by the value after the => select the number in the []. i tried attaching a photo but i'm not sure if it uploaded.
Anyway what i want to do is create a url with id of the next photo and one with the previous photo id in it, so i can have next and previous buttons for my photos.

 

Have you any code? Write here and say what doesn't work in the code.

 

A sloppy (and slow) solution, can't think of a better way atm

$currentpic = ??;
$number = -1;
for($k = 0; $k < count($array); $k++)
{
if($array[$k] == $currentpic)
{
$number = $k;
break;
}
}
if($number == -1)
{
echo 'image 404';
}

PHP:

 

You sure, your code like that?
I do not understand what is mean