Sorting arrays wont show up

        <?php 
include("inc/data.php");
include("inc.functions.php");

$pageTitle = "Full Catalog";
$section = null;

if(isset($_GET["cat"])) {

    if ($_GET["cat"] == "books") {
        $pageTitle = "Books";
        $section = "books";

    } else if ($_GET["cat"] == "movies"){
        $pageTitle = "Movies";
        $section = "movies";

    } else if ($_GET["cat"] == "music"){
        $pageTitle = "Music";
        $section = "music";
    }
}

include("inc/header.php"); ?>

<div class="section catalog page">
    <div class="wrapper">

        <h1> <?php echo $pageTitle; ?></h1>

        <ul class="items">
        <?php 
        $categories = array_category($catalog,$section);
        foreach ($categories as $id) {
            echo get_item_html($id, $catalog[$id]);
        }               
        ?>
        </ul>
    </div>
</div>

<?php include("inc/footer.php"); ?>

<?php
function get_item_html($id,$item) {
$output = "<li><a href='#'><img src='" 
                . $item["img"] . "' alt='" 
                . $item["title"] . "'/>"
                . "<p>View Details</p>"
                . "</a></li>";
        return $output;
}

function array_category($catalog, $category) {
    if ($category == null) {
        return array_keys($catalog);
    }
    $output = array();

    foreach ($catalog as $id => $item) {
        if (strtolower($category) == strtolower($item["category"])) {
            $output[] = $id;

        }
    }

return $output;

}

<?php 
include("inc/data.php");
include("inc/functions.php");
$pageTitle = "Personal Media Library ";

include("inc/header.php"); ?>
        <div class="section catalog random">

            <div class="wrapper">

            <h2>May we suggest something?</h2>

            <ul class="items">
                <?php 
                $random = array_rand($catalog,4);
                foreach ($random as $id) {
                    echo get_item_html($id, $catalog[$id]);

            }
            ?>              
        </ul>

        </div>

        </div>

    <?php include("inc/footer.php"); ?>