hi there i would like to you javascript in my shop so if the user checks a checkbox the site will be reloaded with new values

so here is what i did
JAVASCRIPT

if (!document.getElementsByName("fieldP")[counter].checked){
choice = false;
document.getElementsByName("fieldP" )[0];
location.href= <?php zen_href_link(FILENAME_SHOPPING_CART, 'fieldP=1'); ?>);
}

echo zen_draw_checkbox_field('fieldP', '0', false, 'id="fieldP" onChange="relodWithChangedQty()"');

THE problem is this result :-(
URI/index.php?main_page=shopping_cart&amp;fieldP=1

if it is like this i cant read it out later with $_GET[fieldP] because of the &amp; stuff there

and i saw that all links in the shop from javascript are like this

how can i fix it ?


thx