custom_product_filter

functions.php

<?php 
   add_filter( 'request', 'custom_product_filter' );

    function custom_product_filter( $vars ) {        
        global $wpdb, $pagenow, $typenow, $wp_query, $woocommerce;

		$product_check = '';
		$product_check = $_GET['product_check'];
        
        if ( $typenow == 'shop_order' && isset($product_check) && $product_check > 0 ) :	
			
			$order_id_list   = array();
			$order_id_list[] = 0;			

			$args = array(
    			'numberposts'   => -1,
    			'orderby'       => 'post_date',
    			'order'         => 'desc',
    			'post_type'     => 'shop_order',
    			'post_status'   => 'publish'
			);
			$product_orders = get_posts( $args ); 		
			
			foreach ( $product_orders AS $product_order ) :
				
				$order = &new woocommerce_order( $product_order->ID );
				$items = (array) get_post_meta( $order->id, '_order_items', true );

				foreach($items as $item) :
				
					if ( $item[id] == $product_check ) :
						$order_id_list[] = $order->id;
					endif;
					
				endforeach;
				
			endforeach;

			if ( $order_id_list ) :
				$vars['post__in'] 	= $order_id_list;				
			endif;		
        
        endif;

		return $vars;

    }

    
    add_action('restrict_manage_posts','woocommerce_orders_by_product');
    function woocommerce_orders_by_product() {
        global $typenow, $wp_query;
        if ( $typenow == 'shop_order' ) :
		
			$args = array(
    			'numberposts'     => -1,
    			'orderby'         => 'post_date',
    			'order'           => 'DESC',
    			'post_type'       => 'product',
    			'post_status'     => 'publish' 
			);
			$products = get_posts( $args );

            $output  = "<select name='product_check' id='dropdown_product_check'>";
			$output .= '<option value="">Voucher Filter</option>';
			foreach( $products as $product ) :
            	$output .= '<option value="' . $product->ID . '" ' . selected( $_GET['product_check'], $product->ID, false ) . '>' . $product->post_title . '</option>';
			endforeach;         
            $output .= '</select>';
            
            echo $output;
        
        endif;
    }
?>