xmlUpdateWooCommerce.php

<?php
/**
* copyrights andrew killen 2017
*
* Attribution-ShareAlike 4.0 International. 
**/


/**
* This will get the contents from the db about the current values, optionally if you have setup
* a custom taxonomy you can say "I want from supplier ID n" this helps as SKU's can often be the same
* for many suppliers, it will then load/download an XML file and convert it to an Array, 
* and finally loop through the DB current values, looking for them in the feed array by SKU, if they exist
* then it will try to update the meta, logging ths changes made.
* 
**/
class xmlUpdateWooCommerce {
    // place on the system where CRON downloads the file. this is normally 10 --> 20X faster than php
    protected $fileSystemFile = '/path/to/cron/downloaded/file.xml';
    // fall back to remote url
    protected $feedUrl = "https://somesite.com/feed.xml";
    // where the database current values are held
    protected $result;
    // the XML that is loaded
    protected $xml;

    /**
    * How to run the whole thing.  
    * @param $supplier int, optional tax term id that can be used to define all products from one supplier  
    */
    public function init($supplier = 0){
        $this->getCurrentDbValues($supplier);
        $this->openFeedAsXML();
        $this->feedLoopAndUpdate()
    }

    /**
    * Use $wpdb and a generated select statement to return an object with all
    * of the needed produt meta + product ID
    *
    * @param $supplier int taxonomy term id
    *
    * @return object
    */
    protected function getCurrentDbValues($supplier = 0){
        global $wpdb;
        // set the post type to search through
        $post_type = 'product';
        // postmeta data that will be joined to the result
        $metas = ['_sku','_stock', '_regular_price','_price'];
        // look the metas to add the sql statement to make the joins
        foreach ($metas as $i => $meta_key) {
            $meta_fields[] = 'm' . $i . '.meta_value as ' . $meta_key;
            $meta_joins[] = ' left join ' . $wpdb->postmeta . ' as m' . $i . ' on m' . $i . '.post_id=' . $wpdb->posts . '.ID and m' . $i . '.meta_key="' . $meta_key . '"';
        }
        // begin the SQL statemnt adding in the meta fields to ID
        $request = "SELECT ID, " .  join(',', $meta_fields) . " FROM $wpdb->posts ";
        // add the joins
        $request .=  join(' ', $meta_joins);
        // make sure its using the right post status and post type
        $request .= " WHERE {$wpdb->posts}.post_status='publish' AND {$wpdb->posts}.post_type='{$post_type}'";

        /**
        * Optional, use supplier taxonomy to reduce the total number of records 
        * returned.  This is often needed as SKU's can be the same from many suppliers.
        *
        * It should really double check to see if the term tax id exists first... 
        **/
        if($supplier != 0){
            $request .= " AND ID IN(
                select object_id FROM {$wpdb->prefix}term_relationships where term_taxonomy_id ='{$supplier}'
            )";
        }        
        $this->result = $wpdb->get_results($request);
    }

    /**
    * tries to get CRON downloaded file first
    *
    * Idealy this should check the file datetime to see if it out of date
    *
    * @return void
    **/
    protected function openFeedAsXML(){
        if(file_exists($this->fileSystemFile)){
            $this->xml = simplexml_load_file($this->fileSystemFile, NULL, LIBXML_NOCDATA);
        } else {
            $content = file_get_contents($this->feedUrl);
            $this->xml = simplexml_load_string($content, NULL, LIBXML_NOCDATA);
        }
    }


    /**
     * Loop through the feed XML converting it to an assoicative array
     * where the sku is the key, and the other values are in an array assoicated
     * with it. 
     *
     * this will convert the entire feed, not just the items that are in the db.  
     * becuase of the use late of isset(), it will make it uber fast.
     *
     * If I was making this for anyone else I would have spilt this up a bit into separate methods 
     * and not nested loops, but I love doing it this way. nested loops make me happy :)
     */
    protected function feedLoopAndUpdate(){
        // VidaXL use /products/product to hold the stock items. change this as needed
        $nodes = $this->xml->xpath("/products/product");
        $output = [];
        // This is part of the magic here.  make sure the SKU is the key
        foreach($nodes as $node ){
            $output [(int) $node->SKU] = [
                    'stock' => (int) $node->Stock,
                    'rrp' => (string) $node->RRP,
            ];
        }
        // loop through the result
        foreach( $this->result as $row ){        
            $check = [
                '_stock' => 'stock',
                '_price' => 'rrp' ,
                '_regular_price' =>  'rrp',
            ];

            // check the feed array if the sku exists.  if it does work on it
            if(isset($output[$row->_sku])){
                // loop through the fiels/post meta you can to check
                foreach($check as $meta => $field) {
                    // continue to next meta is this meta does not exist
                    if(empty($row->{$meta})){
                        continue;
                    }
                    // If the current meta value is different to the one in the feed, update.
                    if($output[$row->_sku][$field] != $row->{$meta}){
                        /**
                        * some error logging so you can see what happend
                        */
                        error_log( "ID: {$row->ID} SKU: {$row->_sku} - changing $meta to be: {$output[$row->_sku][$field]} , $meta was: {$row->{$meta}}" );
                        if(is_admin()){
                            echo  "ID: {$row->ID} SKU: {$row->_sku} - changing $meta to be: {$output[$row->_sku][$field]} , $meta was: {$row->{$meta}} ";
                            echo  "<a href='".get_permalink($row->ID)."'>". get_the_title($row->ID) ."</a> <br/>";
                        }
                        /*
                        * update the post meta for that value
                        */ 
                        update_post_meta($row->ID, $meta, $output[$row->_sku][$field]);
        
                    }
                }             
            } else {
                $this->whatToDoIfSKUdoesNotExistInFeed($row->ID);
            }
        }
    }


    protected function whatToDoIfSKUdoesNotExistInFeed($id) {
        // do something like send an email, or create a report that tells
        // the system owner that the product is no longer available in the feed
        // this will stop orphaned products, or products that say they have stock 
        // when the supplier cannot deliver.
    }

}