update_post_meta from data in multidimensional array created from a form

So, I have a few form fields like so:

<input name="mainStageSatOrder[theband][theid]" type="hidden" class="band-id" value="" />";
<input name="mainStageSatOrder[theband][theorder]" type="hidden" class="band-order" value="" />";

As you can see, these form fields (of which there are more, these are just examples of both types) create a multi-dimensional array like so (I hope, please correct me if I’m wrong):

Array (
[mainStageSatOrder] => Array
    (
        [theband] => Array
            (
                [theid] => 1
                [theorder] => 5
            )

        [theband] => Array
            (
                [theid] => 2
                [theorder] => 8
            )
    )
)

I want these values to use the update_post_meta function to update the relevant fields when the page update is submitted. I know I can hook into the submit action post_submitbox_start action which I understand just fine.

What I’m not sure on, is what the PHP might be once the submit button is clicked. What I want to happen is that when the submit button is clicked, the multidimensional array is looped through using a foreach loop and for each ‘theband’ sub-array, the two values are used in the update_post_meta function.

foreach(???) {
    update_post_meta( 1, 'theorder', '5' ); //where 1 and 5 are values passed from the MD array
}

So, the process goes:

1) User clicks publish/update button
2) All values from all fields are passed into the multidimensional array
3) The MD array is looped through and, using update_post_meta, the relavent data is updated
4) Confirm yes/no

Thanks.

First off, there’s a problem with your array. Arrays can not have duplicate keys. So, only the first key will be saved. You need to change your form to something like this.

<input name="mainStageSatOrder[theband0][theid]" type="hidden" class="band-id" value="" />";
<input name="mainStageSatOrder[theband0][theorder]" type="hidden" class="band-order" value="" />";
<input name="mainStageSatOrder[theband1][theid]" type="hidden" class="band-id" value="" />";
<input name="mainStageSatOrder[theband1][theorder]" type="hidden" class="band-order" value="" />";

The array will look like this

$array = array(
    'mainStageSatOrder' => array(
        'theband0' => array(
            'theid' => 1,
            'theorder' => 5
        ),
        'theband1' => array(
            'theid' => 2,
            'theorder' => 8
        )
    )
);

You don’t need a foreach loop while saving the meta data. You can instead save it as an array. WordPress will automatically serialize it for you.

$array = $_POST['mainStageSatOrder'];
update_post_meta( $postid, 'mainStageSatOrder', $array );  

And, while retriving the values..

$data = get_post_meta($post->ID, 'mainStageSatOrder', true);  

The returned $data will be an array.