compareFolderItems.php

<?php

function compareFolderItems($a, $b) {

    if (is_dir($a) && is_dir($b)) {
        return strnatcasecmp($a, $b);
    }

    if (is_file($a) && is_file($b)) {

        $compareExtensions = strcasecmp(
            pathinfo($a, PATHINFO_EXTENSION),
            pathinfo($b, PATHINFO_EXTENSION)
        );

        if ($compareExtensions === 0) {
            return strnatcasecmp($a, $b);
        }
        
        return $compareExtensions;
    }

    if (is_dir($a) && is_file($b)) return -1;
    if (is_file($a) && is_dir($b)) return 1;
}


function listFolderItems($folder) {

    chdir($folder);

    // Get directory items
    $items = array_diff(scandir('.'), array('.', '..', '.DS_Store'));

    // Folders, type and alphabetically
    usort($items, 'compareFolderItems');

    return $items;
}

$items = listFolderItems('content');