Determine if a user is active or not for a specific product

mp_active.php

<?php

/** Returns true if a specified user is active for a specified product ... false if the user isn't active */
function is_user_active_for_product( $user_id, $product_id ) {
  global $wpdb;
  $mepr_db = new MeprDb();

  $sql = "SELECT COUNT(*) " .
           "FROM {$mepr_db->transactions} " .
          "WHERE user_id=%d " .
            "AND product_id=%d " .
            "AND ( expires_at='0000-00-00 00:00:00' " .
                  "OR expires_at > NOW() )";

  $sql = $wpdb->prepare( $sql, $user_id, $product_id );

  $active_transaction_count = $wpdb->get_var($sql);

  return !empty($active_transaction_count);
}

/** Returns an array of user ids of active users for a given product */
function active_users_for_product( $product_id ) {
  global $wpdb;
  $mepr_db = new MeprDb();

  $sql = "SELECT user_id " .
           "FROM {$mepr_db->transactions} " .
          "WHERE product_id=%d " .
            "AND ( expires_at='0000-00-00 00:00:00' " .
                  "OR expires_at > NOW() )";

  $sql = $wpdb->prepare( $sql, $product_id );

  $user_ids = $wpdb->get_col( $sql );

  return $user_ids;
}