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

main.php

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

$callStartTime = microtime(true);

$objPHPExcel =  PHPExcel_IOFactory::load('multipage.xls');

$sheetsIterator = $objPHPExcel->getWorksheetIterator();

$tmpFileName = microtime(true);

while( $sheetsIterator->valid()) {

    // Create new object to write converted data and separate documents sheets
    $csvPagePhpExcel = new PHPExcel();
    $sheet = $sheetsIterator->current();
    $csvPagePhpExcel->addSheet($sheet, 0);

    // Creating CSV writer Object and save data to file
    $objWriter = PHPExcel_IOFactory::createWriter($csvPagePhpExcel, 'CSV');

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

    $sheetsIterator->next();
}

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

nice!