headers.php

<?php

// no cache
if (!headers_sent()) {
    header('Expires: Wed, 11 Jan 1984 05:00:00 GMT');
    header('Last-Modified: ' . gmdate('D, d M Y H:i:s') . ' GMT');
    header('Cache-Control: no-cache, must-revalidate, max-age=0');
    header('Pragma: no-cache');
}

// download
if (!headers_sent()) {
    // Required for some browsers
    if (ini_get('zlib.output_compression')) {
        @ini_set('zlib.output_compression', 'Off');
    }

    header('Pragma: public');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');

    // Required for certain browsers
    header('Cache-Control: private', false);

    header('Content-Disposition: attachment; filename="' . basename(str_replace('"', '', $filename)) . '";');
    header('Content-Type: application/force-download');
    header('Content-Transfer-Encoding: binary');

    if ($content) {
        header('Content-Length: ' . strlen($content));
    }

    ob_clean();
    flush();

    if ($content) {
        echo $content;
    }
}

// utf8
if (!headers_sent()) {
    header('Content-type: text/html; charset=utf-8');
}