Estoy intentando crear un archivo csv para actualizar mi inventario en Magento. Mi código es el siguiente:

    <?php
require_once ('../db.php');

$conn = db_connect();
$inventory = array();
$csvContent = "";
$n=0;


$result = $conn->query("select inventory.sku, book.author, book.title,
 book.publisher,     book.pub_date, book.edition,
inventory.isbn13, book.binding, book_condition.book_condition, defect.defect, note,    
feature, inventory.ourPrice, inventory.cost, inventory.quantity, subtitle, weight
from inventory
LEFT JOIN book on book.isbn13 = inventory.isbn13
LEFT JOIN defect on inventory.defect_id = defect.defect_id
LEFT JOIN note on inventory.note_id = note.note_id
LEFT JOIN feature on inventory.feature_id = feature.feature_id
LEFT JOIN book_condition on book_condition.condition_id = defect.condition_id
where inventory.quantity >0");

$num_rows = $result->num_rows;

if($num_rows > 0)
{ 
while($row = $result->fetch_assoc())
{
$inventory[$n] = array('sku' => $row['sku'],
        'author' => $row['author'],
                    /*'title' => $row['title'],
                    'publisher' => $row['publisher'],
                    'pub_date' => $row['pub_date'],
                    'edition' => $row['edition'],
                    'publisher' => $row['publisher'],
                    //'isbn10' => $isbn10,
                    'isbn13' => $row['isbn13'],
                    'binding' => $row['binding'],
                    'condition' => $row['condition'],
                    'defects' => $row['defect'],
                    'notes' => $row['note'],
                    'feature' => $row['feature'],
                    'price' => number_format($row['ourPrice'], 2, '.', ''),
        'cost' => $row['cost'],
                    'description' => $row['defect'],
                    'quantity' => $row['quantity'],
        'store' => "default",
        'websites' => "base",
        'attribute_set' => "books",
        'type' => "simple",
        'category' => "6",
        'type' => "simple",
        'image' => "/bcpics/".$row['isbn13'].".gif",
        'small_image' => "/bcpics/".$row['isbn13'].".gif",
        'thumbnail' => "/bcpics/".$row['isbn13'].".gif",
        'page_layout' => "No Layout updates",
        'options_container' => "Block after Info Column",
        'weight' => $row['weight'],
            'status' =>"Enables",
        'tax_class_id' =>"Taxable Goods", 
        'visibility'  =>"Catalog, Search",
        'enable_googlecheckout'  =>"yes",
        'is_recurring'  =>"no",
        'min_qty'  =>"0",*/
        'use_config_min_qty' =>"1",
        'is_qty_decimal'  =>"0",
        'backorders'  =>"0",
        'use_config_backorders' =>"1",
        'min_sale_qty' =>"1",
        'use_config_min_sale_qty' =>"1",
        'max_sale_qty'  =>"0",
        'use_config_max_sale_qty' =>"1",
        'is_in_stock' =>"1",
        'use_config_notify_stock_qty' =>"1",
        'manage_stock' =>"0",
        'use_config_manage_stock' =>"1",
        'stock_status_changed_automatically' =>"0",
        'use_config_qty_increments' =>"1",
        'qty_increments' =>"0",
        'use_config_enable_qty_increments' =>"1",
        'enable_qty_increments' =>"0",
        'store_id' =>"1",
        'product_type_id' =>"simple",
        'add_delete' => "",
        'url_key' => "",
        'gift_message_available' => "",
        'Topic' => "",
        'Subtitle'=> $row['subtitle'],
        'meta_title' => "",
        'meta_description' => "",
        'custom_design' => "",
        'url_path' => "",
        'special_price' => "",
        'meta_keyword' => "",
        'custom_layout_update' => "",
        'news_from_date' => "",
        'news_to_date' => "",
        'special_from_date' => "",
        'special_to_date' => "",
        'custom_design_from' => "",
        'custom_design_to' => "",
        'low_stock_date' => "",
        'notify_stock_qty' => "",
        'product_status_changed' => "",
        'product_changed_websites'=> "",
        'has_options'=> "0"

            );
    //print_r($inventory);die;
    $n++;
    } //end of while loop
} // end of if statement

$csvInventory = to_csv($inventory);

function to_csv( $array ) {
 $csv = "";

 if (count($array) == 0) return "No SKU's found";

 ## Grab the first element to build the header
 $arr = array_pop( $array );
 $temp = array();
 foreach( $arr as $key => $data ) {
   $temp[] = $key;
 }
 $csv = implode( ',', $temp ) . "\r\n";

 ## Add the data from the first element
 $csv .= to_csv_line( $arr );

 ## Add the data for the rest
 foreach( $array as $arr ) {
   $csv .= to_csv_line( $arr );
 }

 return $csv;
}

function to_csv_line( $array ) {
 $temp = array();
 foreach( $array as $elt ) {
   $temp[] = '"' . addslashes( $elt ) . '"';
 }

 $string = implode( ',', $temp ) . "\r\n";

 return $string;
}

$conn->close();

$myFile = "/home/bookcell/public_html/testbcos/web/inv/BCWebsite" . date("mdY") . ".csv";
$fh = fopen($myFile, 'w') or die("can't open file");
$stringData = $csvInventory;
fwrite($fh, $stringData);
fclose($fh);

Mi problema es que no puedo hacer que funcione si intento usar todos los parámetros en el$inventory[$n] = array(). Puedo hacer que todas las filas de la matriz, excepto unas 30, funcionen al mismo tiempo, actualmente todo en el/* y*/ no trabajará. He jugado cambiando los campos entre/* y*/ así que sé que cada fila entrará en el csv sin ningún problema. He comprobado los registros de errores en mi servidor y no hay ningún error, y el registro de transferencia muestra que debería estar funcionando. ¿Alguien ve donde me voy mal aquí? ¿Hay una mejor manera de hacerlo que obtenga los resultados que necesito?