Fetch the Ordered Products through collection

I Have modified your code please use below code and you will get all customer orders in csv file.

<?php
require_once('app/Mage.php');
error_reporting(E_ALL);
ini_set('display_errors', 'On');
umask(0);
if (!Mage::isInstalled()) {
    echo "Application is not installed yet, please complete install wizard first.";
    exit;
}
// Only for urls // Don't remove this
$_SERVER['SCRIPT_NAME'] = str_replace(basename(__FILE__), 'index.php', $_SERVER['SCRIPT_NAME']);
$_SERVER['SCRIPT_FILENAME'] = str_replace(basename(__FILE__), 'index.php', $_SERVER['SCRIPT_FILENAME']);
Mage::app('admin')->setUseSessionInUrl(false);
Mage::setIsDeveloperMode(true); ini_set('display_errors', 1); error_reporting(E_ALL);
try {
    Mage::getConfig()->init();
    Mage::app();  
} catch (Exception $e) {
    Mage::printException($e);
}
ini_set('memory_limit','500M');
$customerCount = 0;
try{
    //configure the collection filters.
    $collection = Mage::getResourceModel('customer/customer_collection')
    ->addAttributeToSelect('entity_id')
    ->addAttributeToSelect('firstname')
    ->addAttributeToSelect('email');

    //Add a page size to the result set.
    $collection->setPageSize(50);
    //discover how many page the result will be.
    $pages = $collection->getLastPageNumber();
    $currentPage = 1;
    //This is the file to append the output to.
    $fp = fopen('customers.csv', 'w');
    $header=array("Customer Id","First name",'Email',"order id","order date","products","product create time");
    fputcsv($fp, $header);
    do{
         //Tell the collection which page to load.
         $collection->setCurPage($currentPage);
         $collection->load();
         foreach ($collection as $customer){
             $customerArray = $customer->toArray();

  $newordercollection = Mage::getModel("sales/order")->getCollection()->addFieldToFilter('customer_id',$customerArray['entity_id']);     

  $collection->setOrder('entity_id', 'ASC');
  $ordervalue = $newordercollection->getFirstItem();

        // get product information
        $result=array();
        $customerREquiredArray=array();
        foreach ($ordervalue->getAllVisibleItems() as $item)
          {  
            $createdAt = $ordervalue->getCreatedAt();
            $myTimezone = new \DateTimeZone("Asia/Kolkata");
            $UTC = new DateTimeZone("UTC");
            $newDate = new \DateTime( $createdAt, $UTC );
            $newDate->setTimezone( $myTimezone );
            $createdAt = $newDate->format('Y-m-d H:i:s');

            $productCreatedAt=$item->getProduct()->getCreatedAt();
            $pNewdate = new \DateTime( $productCreatedAt, $UTC );
            $pNewdate->setTimezone( $myTimezone );
            $productCreatedAt = $pNewdate->format('Y-m-d H:i:s');


            $sku = $item->getSku();
            $eid = $ordervalue->getOrderId();  
            $order = Mage::getModel("sales/order")->load($eid);
            $customerREquiredArray['customer ID'] = $customerArray['entity_id'];
            $customerREquiredArray['First name'] = $customerArray['firstname'];
            $customerREquiredArray['Email'] = $customerArray['email'];          
            $customerREquiredArray['order id']= $ordervalue->getIncrementId();          
            $customerREquiredArray['order date']= $createdAt;          
            $customerREquiredArray['products']= $sku;
            $customerREquiredArray['product create time']= $productCreatedAt;
            fputcsv($fp, $customerREquiredArray);
            break;
        }      
        }
            $currentPage++;
            $customerCount++;
         $collection->clear();
         echo "Finished page $currentPage of $pages \n";
    } while ($currentPage <= $pages);
    fclose($fp);
} catch (Exception $e) {
    Mage::printException($e);
}
echo "Saved $customerCount customers to csv file \n";

Here is output

I have updated your problematic code check.

foreach ($ordervalue->getAllVisibleItems() as $item)
          {  
            $sku[] = $item->getSku(); //set sku in array
          }      
          $eid = $ordervalue->getOrderId();  
          $order = Mage::getModel("sales/order")->load($eid);

    }
        //write the collection array as a CSV.

        $customerREquiredArray['customer ID'] = $customerArray['entity_id'];
        $customerREquiredArray['First name'] = $customerArray['firstname'];
        $customerREquiredArray['Email'] = $customerArray['email'];          
        $customerREquiredArray['order id']= $orderID;          
        $customerREquiredArray['order date']= $createdAt;          
        $customerREquiredArray['products']=  implode(",",$sku); // convert array to string