Почему переопределение default_addtocart.php приводит к поломке?? - [VM2&3] Модификации и хаки

<?php
/**
defined('_JEXEC') or die('Restricted access');
if (isset($this->product->step_order_level))
	$step=$this->product->step_order_level;
else
	$step=1;
if($step==0)
	$step=1;
$alert=JText::sprintf ('COM_VIRTUEMART_WRONG_AMOUNT_ADDED', $step);

//bng347-32 наверно нижеследующую функцию лучше вывести в require_once ...
function TransUrl($str)
    {
        $tr = array(
            "А"=>"a",
            "Б"=>"b",
            "В"=>"v",
            "Г"=>"g",
            "Д"=>"d",
            "Е"=>"e",
            "Ё"=>"e",
            "Ж"=>"j",
            "З"=>"z",
            "И"=>"i",
            "Й"=>"y",
            "К"=>"k",
            "Л"=>"l",
            "М"=>"m",
            "Н"=>"n",
            "О"=>"o",
            "П"=>"p",
            "Р"=>"r",
            "С"=>"s",
            "Т"=>"t",
            "У"=>"u",
            "Ф"=>"f",
            "Х"=>"h",
            "Ц"=>"ts",
            "Ч"=>"ch",
            "Ш"=>"sh",
            "Щ"=>"sch",
            "Ъ"=>"",
            "Ы"=>"i",
            "Ь"=>"j",
            "Э"=>"e",
            "Ю"=>"yu",
            "Я"=>"ya",
            "а"=>"a",
            "б"=>"b",
            "в"=>"v",
            "г"=>"g",
            "д"=>"d",
            "е"=>"e",
            "ё"=>"e",
            "ж"=>"j",
            "з"=>"z",
            "и"=>"i",
            "й"=>"y",
            "к"=>"k",
            "л"=>"l",
            "м"=>"m",
            "н"=>"n",
            "о"=>"o",
            "п"=>"p",
            "р"=>"r",
            "с"=>"s",
            "т"=>"t",
            "у"=>"u",
            "ф"=>"f",
            "х"=>"h",
            "ц"=>"ts",
            "ч"=>"ch",
            "ш"=>"sh",
            "щ"=>"sch",
            "ъ"=>"y",
            "ы"=>"i",
            "ь"=>"j",
            "э"=>"e",
            "ю"=>"yu",
            "я"=>"ya",
            " "=> "_",
            "."=> "",
            "/"=> "_",
            ","=>"_",
            "-"=>"_",
            "("=>"",
            ")"=>"",
            "["=>"",
            "]"=>"",
            "="=>"_",
            "+"=>"_",
            "*"=>"",
            "?"=>"",
            "\""=>"",
            "'"=>"",
            "&"=>"",
            "%"=>"",
            "#"=>"",
            "@"=>"",
            "!"=>"",
            ";"=>"",
            "№"=>"",
            "^"=>"",
            ":"=>"",
            "~"=>"",
            "\\"=>""
        );
        return strtr($str,$tr);
    }
//bng347-32 end
?>

<div class="addtocart-area">

	<form method="post" class="product js-recalculate" action="<?php echo JRoute::_ ('index.php',false); ?>">
		<input name="quantity" type="hidden" value="<?php echo $step ?>" />
		<?php // Product custom_fields
		if (!empty($this->product->customfieldsCart)) {
			?>
			<div class="product-fields">
				<?php foreach ($this->product->customfieldsCart as $field) { ?>
				<div class="product-field product-field-type-<?php echo $field->field_type ?>">
					<?php if ($field->show_title) { ?>
						<span class="product-fields-title-wrapper"><span class="product-fields-title"><strong><?php echo vmText::_ ($field->custom_title)?></strong></span>
					<?php }
					if ($field->custom_tip) {
						echo JHTML::tooltip (vmText::_($field->custom_tip), vmText::_ ($field->custom_title), 'tooltip.png');
					} ?></span>
					<span class="product-field-display">
						<?php /*bng347-11 bng347-28 bng347-32*/
						if($field->custom_title=="Тип багета"||$field->custom_title=="Цвет"||$field->custom_title=="Размер"){
							$key = key($this->product->customfieldsCart);
							$options = $field->options;
							//echo TransUrl($field->custom_title);
							  ?>
							  <select name="<?php echo "customPrice[$key][$field->virtuemart_custom_id]";  ?>" required class="<?php echo TransUrl($field->custom_title);?>_select">
								 <option disabled selected><?php echo $field->custom_title;?></option>
								 <?php foreach($options as $option){
									echo '<option value="'.$option->virtuemart_customfield_id.'">'.$option->custom_value.'</option>';
								 }
								 ?>
							  </select>
						<?php }
						else { echo $field->display;}
						/*bng347-11 bng347-28 bng347-32 end */
						?>
					</span>
					<span class="product-field-desc"><?php echo vmText::_($field->custom_field_desc)?></span>
				</div><br/>
				<?php } ?>
			</div>
			<?php
		}
		/* Product custom Childs
			 * to display a simple link use $field->virtuemart_product_id as link to child product_id
			 * custom_value is relation value to child
			 */

		if (!empty($this->product->customsChilds)) {
			?>
			<div class="product-fields">
				<?php foreach ($this->product->customsChilds as $field) { ?>
				<div class="product-field product-field-type-<?php echo $field->field->field_type ?>">
					<span class="product-fields-title"><strong><?php echo JText::_ ($field->field->custom_title)?></strong></span>
					<span class="product-field-desc"><?php echo JText::_ ($field->field->custom_value)?></span>
					<span class="product-field-display"><?php echo $field->display ?></span>

				</div><br/>
				<?php } ?>
			</div>
		<?php
		}

		if (!VmConfig::get('use_as_catalog', 0)  ) {
		?>

		<div class="addtocart-bar">

<script type="text/javascript">
		function check(obj) {
 		// use the modulus operator '%' to see if there is a remainder
		remainder=obj.value % <?php echo $step?>;
		quantity=obj.value;
 		if (remainder  != 0) {
 			alert('<?php echo $alert?>!');
 			obj.value = quantity-remainder;
 			return false;
 			}
 		return true;
 		}
</script> 

		<?php // Display the quantity box

			$stockhandle = VmConfig::get ('stockhandle', 'none');
			if (($stockhandle == 'disableit' or $stockhandle == 'disableadd') and ($this->product->product_in_stock - $this->product->product_ordered) < 1) {
				?>
				<a href="<?php echo JRoute::_ ('index.php?option=com_virtuemart&view=productdetails&layout=notify&virtuemart_product_id=' . $this->product->virtuemart_product_id); ?>" class="notify"><?php echo JText::_ ('COM_VIRTUEMART_CART_NOTIFY')?></a>
				<?php
			} else {
				$tmpPrice = (float) $this->product->prices['costPrice'];
				if (!( VmConfig::get('askprice', 0) and empty($tmpPrice) ) ) {
					?>
					<!-- <label for="quantity<?php echo $this->product->virtuemart_product_id; ?>" class="quantity_box"><?php echo JText::_ ('COM_VIRTUEMART_CART_QUANTITY'); ?>: </label> -->
					<span class="quantity-box">
						<input type="text" class="quantity-input js-recalculate" name="quantity[]" onblur="check(this);"
							   value="<?php if (isset($this->product->step_order_level) && (int)$this->product->step_order_level > 0) {
									echo $this->product->step_order_level;
								} else if(!empty($this->product->min_order_level)){
									echo $this->product->min_order_level;
								}else {
									echo '1';
								} ?>"/>
					</span>
					<span class="quantity-controls js-recalculate">
					<input type="button" class="quantity-controls quantity-plus"  />
					<input type="button" class="quantity-controls quantity-minus" />
					</span>
					<?php // Display the quantity box END

					// Display the add to cart button ?>
          			<span class="addtocart-button">
          			<?php echo shopFunctionsF::getAddToCartButton ($this->product->orderable);
						// Display the add to cart button END  ?>
         			 </span>
					<noscript><input type="hidden" name="task" value="add"/></noscript>
					
				<?php
				}
				?>
			<?php
			}
			?>
			<div class="clear"></div>
		</div>
		<?php
		}
		?>
		<input type="hidden" name="option" value="com_virtuemart"/>
		<input type="hidden" name="view" value="cart"/>
		<input type="hidden" name="virtuemart_product_id[]" value="<?php echo $this->product->virtuemart_product_id ?>"/>
		<input type="hidden" class="pname" value="<?php echo htmlentities($this->product->product_name, ENT_QUOTES, 'utf-8')?>"/>
	</form>
	<div class="clear"></div>
</div>

$this->product = $product;

$lang = JLanguage::getInstance('ru-RU');
$lang->transliterate($string);