optimized example for http://habrahabr.ru/post/269051/

main.php

<?php
require 'vendor/autoload.php';

$callStartTime = microtime(true);

$filename = "multipage.xls";
$objReader = PHPExcel_IOFactory::createReaderForFile($filename);
$objReader->setReadDataOnly(true);
$objPHPExcel =  $objReader->load($filename);;

$sheetsIterator = $objPHPExcel->getWorksheetIterator();

$tmpFileName = microtime(true);

// Creating CSV writer Object and save data to file
$objWriter = new PHPExcel_Writer_CSV($objPHPExcel);
while( $sheetsIterator->valid()) {

    $objWriter->setSheetIndex($sheetsIterator->key());

    $currentTmpFileName = "{$tmpFileName}_sheet_{$sheetsIterator->key()}.csv";
    $objWriter->save($currentTmpFileName);

    $sheetsIterator->next();
}

$callEndTime = microtime(true);
$callTime = $callEndTime - $callStartTime;
echo "\n" . $callTime . "\n";

nice!