PHP – Array from form – WordPress Metadata

I got a custom post type, with a form for storing some data (name, url) to display in a template.

What I want to know is how can I store those values in an array?

An example of my code:

<? function files_metadata(){
        global $post;
        $custom = get_post_custom($post->ID);
        $name = $custom["name"][0];
        $url = $custom["url"][0];

        echo '<input type="hidden" name="files_metadata" id="files_metadata" value="' .wp_create_nonce('files_m'). '" />'; ?>  

<label>Name: </label><br/>
<input id="name" name="name" value="<?php echo $name; ?>" />
<label>Url: </label><br/>
<input id="url" name="url" value="<?php echo $url; ?>" />

<? function save_meta_files($post_id) {
        if (!wp_verify_nonce($_POST['files_metadata'], 'files_m')) return $post_id;
        if (defined('DOING_AUTOSAVE') && DOING_AUTOSAVE) return $post_id;

        update_post_meta($post_id, "name", $_POST["url"]);
        update_post_meta($post_id, "url", $_POST["url"]);
    }  

add_action('save_post', 'save_meta_files'); ?>

To this I want to add something like…

$url = $custom["url"][0];
$url2 = $custom["url"][1];
$url3 = $custom["url"][2];

<input id="url" name="url[0]" value="<?php echo $url; ?>" />
<input id="url2" name="url[1]" value="<?php echo $url2; ?>" />
<input id="url3" name="url[2]" value="<?php echo $url3; ?>" />

update_post_meta($post_id, "url", $_POST["url"][0]);
update_post_meta($post_id, "url2", $_POST["url"][1]);
update_post_meta($post_id, "url3", $_POST["url"][2]);

…but that actually works…

I hope you understand me,
Thanks for your time