Download a file [PHP]

download_file.php

<?php
/**
 * Download a file
 * 
 * @param string $file
 * @return void
 */
function download_file( $file )
{
	if ( file_exists($file) && $file != $_SERVER['DOCUMENT_ROOT'] ) {
		header('Content-Description: File Transfer' );
		header('Content-Type: application/octet-stream' );
		header( 'Content-Disposition: attachment; filename=' . basename( $file ) );
		header( 'Expires: 0' );
		header( 'Cache-Control: must-revalidate' );
		header( 'Pragma: public' );
		header( 'Content-Length: ' . filesize( $file ) );
		ob_clean();
		flush();
		readfile( $file );
	}
}