WooCommerce - Remove alt texts

<?php
  // function to slice out alt texts from WooCommerce images
  // code goes in functions.php for your child theme

  // echo apply_filters( 'woocommerce_single_product_image_html', sprintf( '<a href="%s" itemprop="image" class="woocommerce-main-image zoom" title="%s" data-rel="prettyPhoto' . $gallery . '">%s</a>', $image_link, $image_caption, $image ), $post->ID );

  add_filter ('woocommerce_single_product_image_html', 'my_function');
  function my_function($html) {
   $start = stripos($html, 'alt="');
    if ($start) {
      $end = stripos($html, '"', $start + 5);
      $html = substr($html, 0, $start - 1).substr($html, $end + 1);
    }
    return $html;
  }