Complicated array, how would I set this up and check values against it?

Question

My data pulling looks like this so far:

<?php
    include '/classes.php';
    include '/icon_ids.php';
    $conndb = new conndb($db_host, $db_port,$db_user, $db_pass, $db_name);
    $data = new data($conndb);
    echo $findDisplayIcon[$data->getDisplayID($data->getMainBackpack[23]['entryid']));
?>

Overview: I'm finding an ItemID# in a backpack, getting the displayID# of it from the items table, and then wanting to find it's Icon/Image with its # using $findDisplayIcon and do not know how to setup $findDisplayIcon.

What i'm having trouble with: once I get the displayID#, compare this value, and if it's true in any segment of the array, then it equals this image. Like for example:

$findDisplayID = Array("displayID#1","displayID#2" => "image.png");

nothing prints with this. I do get the displayID to show, so it all works, except this array, or atleast what I am trying to do...