Compress cached output using PHP output buffers

Question

By using this one line code ob_start('ob_gzhandler'); at the top of the page, the php output was about 11 kb according to Chrome console. When I tried to cache the output with the following code, I found the cached file was saved about 65kb. Is the bigger output size the trade off for caching? Is there any way to compress the cached output further? I have tried adding some htaccess rules for html compression but I don't think that helps.

$id = $_GET["id"];
$cachefile ="cache/p_{$id}.html";
if (file_exists($cachefile)) {
 include($cachefile);
 echo "<!-- Cached ".date('jS F Y H:i', filemtime($cachefile))." -->";
 exit;
}
ob_start('ob_gzhandler');

$fp = fopen($cachefile, 'w'); // open the cache file for writing
fwrite($fp, ob_get_contents()); // save the contents of output buffer to the file
fclose($fp); // close the file
ob_end_flush(); 

Answer 1

Your cached file was not gziped by the server, try this way:

ob_start('ob_gzhandler');
$id = $_GET["id"];
$cachefile ="cache/p_{$id}.html";
if (file_exists($cachefile)) {
    include($cachefile);
    echo "<!-- Cached ".date('jS F Y H:i', filemtime($cachefile))." -->";
} else {
    // your html or something else ...
    $fp = fopen($cachefile, 'w'); // open the cache file for writing
    fwrite($fp, ob_get_contents()); // save the contents of output buffer to the file
    fclose($fp); // close the file
}
ob_end_flush(); 

p.s. I would leave this task of compressing to the web server (nginx, apache).