При отправке данных через ajax 500-я ошибка

jQuery(document).ready(function(){ 
        jQuery('.available-btn').click(function(){ 
            var room_type = jQuery(this).attr('data-room-type'); 
            localStorage.setItem('room_type', room_type); 
            jQuery.ajax({ 
            type: "POST", 
            url: "<?php echo get_site_url();?>/wp-content/themes/travelassist/woocommerce/cart/cart.php", 
            data: {room_type:localStorage.getItem('room_type')}, 
            success: function(data) { 
                alert("hi"); 
            } 
          }); 
        }) 
    });