php push zip file to user,and delete in the server

<?php
if (isset ( $_GET ['fetchAll'] ) && ! empty ( $_GET ['fetchAll'] )) {
//$file is like a container,tempnam is very interesting
	$file = tempnam ( "tmp", "zip" );
	$zip = new ZipArchive ();
	$zip->open ( $file, ZipArchive::OVERWRITE );
	$fileDir = dirname ( __FILE__ ) . "/../../download_files/";
//slice '.'& '.'
	$xlses = array_slice ( scandir ( $fileDir ), 2 );
	foreach ( $xlses as $xls ) {
		$zip->addFile ( $fileDir . $xls, $xls );
	}
	$zip->close ();
	header ( 'Content-Type: application/zip' );
	header ( 'Content-Length: ' . filesize ( $file ) );
	header ( 'Content-Disposition: attachment; filename="file.zip"' );
	readfile ( $file );
	unlink ( $file );
}