$filename='invoice.xlsx';
header('Content-Type: application/vnd.openxmlformats-officedocument.excelprocessingml.document');
header('Content-Disposition: attachment;filename="'.$filename.'"');
header('Cache-Control: max-age=0'); //no cache
$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
$objWriter->save('php://output');
die();
header('Content-Type', 'text/vnd.ms-excel; charset=utf-8');
#include <iostream>
#include <cstdio>
#include <ctime>
int main() {
std::clock_t start;
double duration;
start = std::clock();
/* Сюда вставить тестируемый код */
duration = ( std::clock() - start ) / (double) CLOCKS_PER_SEC;
std::cout<<"printf: "<< duration <<'\n';
}