Codeigniter Page cache with GET parameter - codeigniter

Question

I am newbie to CI cache. I am facing some weird problem with codeigniter page caching. $this->output->cache(300);
I was expecting that cached version would not load if arguments in GET[] would change. But it is loading cache without considering any GET[] parameters.
I have one page where it says whether comment has been saved or not [via get parameter],
/product/product-name/?saved=true redirecting to same page where comment form is located. But it is not working. How can i invalidate old cache and create new one depending upon the get parameter? or i need to change the behavior of my comment system?
Thanks.
EDIT
Should i simply use database cache instead of Web page cache in this case?

Answer 1

You just have to enable the cache_query_string option in the config/config.php file.
$config['cache_query_string'] = TRUE;

Answer 2

Create a cache_override hook to check if there are any GET[] variables set and then skip the cache_override.
[EDIT #1]
Here is an example:
Create this file in your hooks directory:
<?php
class GetChecker {
public function checkForGet()
{
global $OUT, $CFG, $URI;
if (isset($_GET) AND ! empty($_GET))
{
return;
}
if ($OUT->_display_cache($CFG, $URI) == TRUE)
{
exit;
}
}
}
Then add this to the config/hooks.php:
$hook['cache_override'][] = array(
'class' => 'GetChecker',
'function' => 'checkForGet',
'filename' => 'GetChecker.php',
'filepath' => 'hooks'
);
I haven't tested it, it might need a little tweaking to work...

Answer 3

I test on CI 3+ , file system/core/Output.php 559 line, change this
if ($CI->config->item('cache_query_string') && !empty($_SERVER['QUERY_STRING']))
{
$uri .= '?'.$_SERVER['QUERY_STRING'];
}
on this
if ($CI->config->item('cache_query_string') /* && ! empty($_SERVER['QUERY_STRING']) */ && !empty($_REQUEST))
{
// $uri .= '?'.$_SERVER['QUERY_STRING'];
$uri .= '?'.http_build_query($_REQUEST);
}
And add string to your application/config/config.php
$config['cache_query_string'] = true;
it will be work with GET, POST, COOKIE ....
If need only GET, just $config['cache_query_string'] = true; - enough

Answer 4

I found no easier way using Hooks to prevent writing cache, as its calling _write_cache() inside the _display() method itself of CI_Output class.
For quick and easiest solution I added two conditions to display cache and write cache, if Query String parameter has variable defined( offset in my case, as I wanted for pagination)
Edit: system/core/Output.php
Add Condition to prevent writing cache, if specific GET parameter found:
function _write_cache($output)
{
if (isset($_GET['offset']) AND ! empty($_GET['offset']))
{
log_message('debug', " Don't write cache please. As as its matching condition");
return;
}
...
...
}
Add Condition to prevent displaying cache, if specific GET parameter found:
function _display_cache(&$CFG, &$URI)
{
if (isset($_GET['offset']) AND ! empty($_GET['offset']))
{
log_message('debug', " Don't display cache please. As as its matching condition");
return FALSE;
}
...
...
}