Custom Metabox Not Saving with looped input box - php

Question

I am creating a metabox that loops through all the posts of another CPT: 'product'. The metabox lists all the published products in that CPT, puts them in a table row along with an input box. Each input box has a unique ID based off of the CPT product id.
Most of this code I have added based on other posts, but I am having a problem saving the data. I know that it has to do with my value="", my nonce, and $meta_value, but I am not sure where to go next. Below is the code I have so far:
<?php
add_action('admin_init', 'my_theme_on_admin_init');
function my_theme_on_admin_init() {
add_meta_box('my_metabox',
__('Daily Inventory Levels', 'textdomain'),
'my_metabox_render',
'location_inventory', 'normal', 'high'
);
}
function my_metabox_render($post) {
// using an underscore, prevents the meta variable
// from showing up in the custom fields section
global $woocommerce, $post;
$productsList = new WP_Query( 'post_type=product&post_status=publish');
?>
<div class="inside">
<table class="form-table">
<input type="hidden" name="inventory_noncename" id="inventory_noncename" value="<?php wp_create_nonce( 'inventory-nonce' ); ?>" />
<?php
while ( $productsList->have_posts() ) {
$productsList->the_post();
?>
<tr><td><label for="location_inventory_product-<?php the_ID(); ?>"><?php the_title(); ?></label></td><td><input id="location_inventory_product-<?php the_ID(); ?>" name="location_inventory_product-<?php the_ID(); ?>" cols="40" rows="5" value="<?php echo $meta_key; ?>" /></td></tr>
<?php }
wp_reset_postdata();
?>
</table>
</div>
<?php
}
/*update on save*/
add_action('save_post', 'save_postdata_dynamic_inventory_metabox' );
function save_postdata_dynamic_inventory_metabox( $post_id ) {
// verify if this is an auto save routine.
// If it is our form has not been submitted, so we dont want to do anything
if ( defined('DOING_AUTOSAVE') && DOING_AUTOSAVE ) {
return;
}
// Check permissions
if ( 'location_inventory' == $_POST['post_type'] ) {
if ( !current_user_can( 'edit_page', $post_id )) {
return $post_id;
}
}
elseif ( !current_user_can( 'edit_post', $post_id )) {
return $post_id;
}
// verify this came from the our screen and with proper authorization,
// because save_post can be triggered at other times
if (isset($_POST['inventory_noncename'])){
if ( !wp_verify_nonce( $_POST['inventory_noncename'], 'inventory-nonce' ) )
return;
} else {
return;
}
// Get the posted data and sanitize it for use as an HTML class.
$new_meta_value = ( isset( $_POST['location_inventory_product-'.the_ID().''] ) ? sanitize_html_class( $_POST['location_inventory_product-'.the_ID().''] ) : '' );
// Get the meta key.
$meta_key = 'location_inventory_product-'.the_ID().'';
// Get the meta value of the custom field key.
$meta_value = get_post_meta( $post_id, $meta_key, true );
// If a new meta value was added and there was no previous value, add it.
if ( $new_meta_value && '' == $meta_value )
add_post_meta( $post_id, $meta_key, $new_meta_value, true );
// If the new meta value does not match the old value, update it.
elseif ( $new_meta_value && $new_meta_value != $meta_value )
update_post_meta( $post_id, $meta_key, $new_meta_value );
// If there is no new meta value but an old value exists, delete it.
elseif ( '' == $new_meta_value && $meta_value )
delete_post_meta( $post_id, $meta_key, $meta_value );
} // ends function save_postdata_dynamic_reviews_metabox

Answer 1

Some observations:
1) The hook save_post takes 2 arguments:
add_action( 'save_post', 'save_postdata_dynamic_inventory_metabox', 10, 2 );
function save_postdata_dynamic_inventory_metabox( $post_id, $post_object ) { }
2) I don't think checking for permissions is necessary (at least, never seen it). Just in case, this is an example of the post_object use:
if ( 'location_inventory' == $post_object->post_type )
3) Short this check:
if ( !isset($_POST['inventory_noncename']) || !wp_verify_nonce( $_POST['inventory_noncename'], 'inventory-nonce' ) )
return;
4) The use of the_ID() inside the function save_postdata_dynamic_inventory_metabox is wrong. This is only available inside a Loop and you already have $post_id at hand.
5) Finally, and the most important, the way you're handling the $meta_key is wrong. For one, it's not defined inside the function my_metabox_render. Check this Answer for a working example.
Research in this search query to find more examples.