Cartelle, ricorsione e array di file trovati

[k.b]

Se vuoi un array che mantenga il formato del tree di directory:

function read_dir_tree($folder) {
    $output = array();
    foreach ( scandir($folder) as $item ) {
        if ( $item == '.' OR $item == '..' )
            continue;
        $full_path = "$folder/$item";
        if ( is_dir($full_path) ) {
            $output[$item] = read_dir_tree($full_path);
        } else {
            $output[] = $full_path;
        }
    }
    return $output;
} 

se invece vuoi la semplice lista "piatta" di tutti i file:

function read_dir_plain($folder) {
    $output = array();
    foreach ( scandir($folder) as $item ) {
        if ( $item == '.' OR $item == '..' )
            continue;
        $full_path = "$folder/$item";
        if ( is_dir($full_path) ) {
            $output = array_merge($output, read_dir_plain($full_path));
        } else {
            $output[] = $full_path;
        }
    }
    return $output;
}