php上载：Fatal error: Allowed memory size of

    function download($filepath, $filename = '') {        if(!$filename) $filename = basename($filepath);        if(is_ie()) $filename = rawurlencode($filename);        $filetype = fileext($filename);        $filesize = sprintf("%u", filesize($filepath));        if(ob_get_length() !== false) @ob_end_clean();        header('Pragma: public');        header('Last-Modified: '.gmdate('D, d M Y H:i:s') . ' GMT');        header('Cache-Control: no-store, no-cache, must-revalidate');        header('Cache-Control: pre-check=0, post-check=0, max-age=0');        header('Content-Transfer-Encoding: binary');        header('Content-Encoding: none');        header('Content-type: '.$filetype);        header('Content-Disposition: attachment; filename="'.$filename.'"');        header('Content-length: '.$filesize);        readfile($filepath);        exit;    }

Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 750743553 bytes) in /var/www/nms/framebase/libs/functions/extention.func.php on line 233