GetPaid Wordpress plugin: Code snippet to synchronise the stock levels of related items (parents, children)

getpaid-sync-related-items-stock.php

<?php
/*
 * When these hooks fire, check each item in the invoice, and set the stock of its parent, children and siblings to the same.
 */

function item_stock_level_sync_dbg_log( $data ) {
	// error_log( print_r( $data, true ) );
}

add_action( 'updated_postmeta', 'sync_related_items_stock_level', 10, 4 );

function sync_related_items_stock_level( $meta_id, $post_id, $meta_key, $meta_value ) {
    if ( $meta_key !== '_stock' || get_post_type( $post_id ) !== 'wpi_item' ) {
        return;
    }

    item_stock_level_sync_dbg_log( "Setting stock of item ID {$post_id} to {$meta_value}" );

    // if this item has a parent and the parent's metadata isn't being updated, just update the meta value of the parent (which will trigger updating of all its children recursively)
    // otherwise, update the stock of all its children (which will trigger updating their children), while indicating this was done by the parent
    $parent = get_post_parent( $post_id );
    if ( $parent && ! get_post_meta( $parent->ID, '_stock_is_locked', true ) ) {
        // it has a parent and this call wasn't triggered by the parent's stock level update => just update the parent's stock
        item_stock_level_sync_dbg_log( "Updating parent only" );
        update_post_meta( $parent->ID, '_stock', $meta_value );
    } else {
        // either no parent, or this call was triggered by the parent's stock level update => ignore parent and siblings, and only update children
        item_stock_level_sync_dbg_log( "Updating children only" );
        update_post_meta( $post_id, '_stock_is_locked', true );
        
        $children = get_children( array(
            'post_parent'    => $post_id,
            'post_type'      => 'wpi_item'
        ) );
        foreach ( $children as $child ) {
            update_post_meta( $child->ID, '_stock', $meta_value );
        }

        update_post_meta( $post_id, '_stock_is_locked', false );
    }
}
?>