bik

abcd0x00

Спасибо болшое. Если в консоле исполняю Ваш пример, все отрабатывается четко.
А вот на оригинальном файле слишком много удаляется:
gross-trading.com/feed.xml

Ориентируюсь по числинности стринга
cat feed.xml|grep '</offer>'|wc -l

Пока пользуюсь этим:

<?php
ignore_user_abort(1);
error_reporting(0);
header("Content-Type: text/html; charset=utf-8");

	$cat = array();
	$xml = new XMLReader();
	$xml->open('./yml - Kopie.xml');
		
	while($xml->read() && $xml->name !== 'category');
		while($xml->name === 'category'){
			$node = new SimpleXMLElement($xml->readOuterXML());
			$id = +$xml->getAttribute("id");
			$name = ''. $node;
			
			$cat[$id] = $name;
			
		$xml->next('category');
		}
	$xml->close();			

//////////////////////////////

	$xml = new XMLReader();
	$xml->open('./yml - Kopie.xml');	
		
	$allparams = array();
	$idparams = array();
	while($xml->read() && $xml->name !== 'offer');
		while($xml->name === 'offer'){
			$node = new SimpleXMLElement($xml->readOuterXML());	
			$id = +$xml->getAttribute("id");
			
			foreach ($node->param as $param){
				$name = ''. $param['name'];
				$value = ''. $param;
				$allparams[] = ''. $param['name'];				
				$idparams[$id][$name] = $value;
			}				
		$xml->next('offer');
		}
	$xml->close();
	
	$allparams = array_unique($allparams);
	sort($allparams);

//////////////////////////////

	$xml = new XMLReader();
	$xml->open('./yml - Kopie.xml');
	$flag = true;	
	while($xml->read() && $xml->name !== 'offer');
		while($xml->name === 'offer'){
			$node = new SimpleXMLElement($xml->readOuterXML());
			
			$id = $xml->getAttribute("id");
			$available = $xml->getAttribute("available");
			$url = $node->url;
			$price = $node->price;
			$currencyId = $node->currencyId;
			$delivery = $node->delivery;
			$local_delivery_cost = $node->local_delivery_cost;
			$typePrefix = $node->typePrefix;
			$vendor = $node->vendor;
			$vendorCode = $node->vendorCode;
			$model = $node->model;
			$description = $node->description;
			$cpa = $node->cpa;
			$weight = $node->weight;
			$pickup = $node->pickup;
			$c = +$node->categoryId;
			$category = $cat[$c];
			
			$picture = '';
			foreach ($node->picture as $pic){
				$picture .= $pic .' ';			   
			}					
			
			if($flag){
				$str = '"id";"Наличие";"url товара";"Цена";"Валюта";"Доставка";"Цена доставки";"Тип";"Производитель";"Код производителя";"Модель";"Описание";"Заказ на маркете";"Вес";"url картинки";"Самовывоз";"Категория";';
				$j = count($allparams);
				while($j-- > 0){
					$str .= '"'. $allparams[$j] .'";';
				}
				$str .= PHP_EOL;
				$str = mb_convert_encoding ($str ,"Windows-1251" , "UTF-8" );			
				$path = fopen("out.csv", "a+");
				fwrite($path, $str);
				fclose($path);
				$flag = false;
			}
			
			$params = '';
			$j = count($allparams);
			while($j-- > 0){				
				$params .= '"'. $idparams[$id][$allparams[$j]] .'";';			
			}		
			
			$str = '"'. $id .'";';
			$str .= '"'. $available .'";';
			$str .= '"'. $url .'";';
			$str .= '"'. $price .'";';
			$str .= '"'. $currencyId .'";';
			$str .= '"'. $delivery .'";';
			$str .= '"'. $local_delivery_cost .'";';
			$str .= '"'. $typePrefix .'";';
			$str .= '"'. $vendor .'";';
			$str .= '"'. $vendorCode .'";';
			$str .= '"'. $model .'";';
			$str .= '"'. $description .'";';
			$str .= '"'. $cpa .'";';
			$str .= '"'. $weight .'";';			
			$str .= '"'. $picture .'";';
			$str .= '"'. $pickup .'";';
			$str .= '"'. $category .'";';
			$str .= $params;
			$str .= PHP_EOL;
			
			$str = mb_convert_encoding ($str ,"Windows-1251" , "UTF-8" );			
			$path = fopen("out.csv", "a+");
			fwrite($path, $str);
			fclose($path);			
			
		$xml->next('offer');
		}
	$xml->close();
gc_enable();
echo 'ok';
?>

Предварительно сокращаю описание товаров:

sed 's#\(<description>\).*\(</description>\)#\1'xxxxx'\2#g' test.xml > test2.xml