private function create_zip( $files = array(), $destination = '', $overwrite = true ) {
		//if the zip file already exists and overwrite is false, return false
		if ( file_exists( $destination ) && ! $overwrite ) {
			return false;
		}

		//create the archive
		$zip = new \ZipArchive();
		if ( $zip->open( $destination, \ZIPARCHIVE::OVERWRITE | \ZIPARCHIVE::CREATE ) !== true ) {
			return false;
		}
		//add the files
		foreach ( $files as $file ) {
			$zip->addFile( $file, basename( $file ) );
		}

		//close the zip -- done!
		$zip->close();

		//check to make sure the file exists
		if ( file_exists( $destination ) ) {
			printf( basename( $destination ) . ' created.' . "\n<br>" );
		} else {
			printf( '<span style="color:#f00">' . basename( $destination ) . ' failed.</span>' . "\n<br>" );
		}
	}