A snippet of code demonstrating how to create a shortcode that will output a number of items sold - This is specific to woocommerce

products_sold_snippet.php

<?php
/* Do not copy the opening <?php tag above */


//Add the shortcode tag with its callback function:
add_shortcode( 'display_tickets_sold', 'wwm_display_tickets_sold' );

/**
 * Given a valid product id, Outputs a number of 'units sold'
 *         Usage [display_tickets_sold product_id="####"] where #### is a valid product id.
 * @param  array $atts an array of shortcode attributes
 * @return void|string returns a formatted html string indicating the number of units sold if the product_id
 *                     is set and the meta key exists and the meta value is not empty. Otherwise, returns void
 */
function wwm_display_tickets_sold( $atts ) {

 if ( ! isset( $atts['product_id'] ) ) {
  return;
 }

 $product_id = absint( $atts['product_id'] );
 $units_sold = get_post_meta( $product_id, 'total_sales', true );
 if ( ! empty( $units_sole ) ) {
  return '<p>' . sprintf( 'Units Sold: %s', $units_sold ) . '</p>';
 }
 return;
}

//You may not need the next line of code:
add_filter( 'widget_text', 'do_shortcode' );