Choosing Caching Systems

[Indifferent]

Which of the following would you say is the best system to use:

1. "Advanced PHP Cache" ACP http://phprpms.sourceforge.net/apc
2. eAccelerator http://eaccelerator.net/ or
3. Memcached http://www.danga.com/memcached/
4. Or maybe something else?

I know people will say that it depends on the situation, but what gives the most features and speed out of the 3.

Or how about in some senarios, which would be the best to use:

1. A blog with regular content and an highly active forum.
2. A portal type of system were users communicate with each other.

How about for this website, sitepoint, what would be the best?
What is used here?

Any advice or tips or whatever would be appreciated.

Thanks in Advance

[Speeple]

eAccelerator is what I use for local cache.

Memcached is a more full blown data cache for databases. Probably overkill.

1) & 2) Both are really database issues, both realtime meaning little caching outside of the database server will be advantageous. Editing the said databases config, data caches etc is what you should be looking into.

[Dan Grossman]

You cannot compare these things and ask which is best. #1 and #2 are both, at the core, code caches. They store precompiled PHP code so it doesn't have to be compiled again next time the same script is run. Not a big difference between the two, but I use APC.

Use APC or eAccelerator. Nobody should run PHP without an opcode cache. I can't imagine why one wasn't built into the PHP engine itself except as a way for Zend to make money selling their accelerator.

Memcached is an object cache. It's for storing information, not code. You could use it with or without a code cache. You might store the results of a complex database query that doesn't need to be run often, for example.

The best thing for your blog is a file cache, not any of these things. If it's so popular you really need to reduce its load, then generate static versions of all the pages and serve those instead of building them on each request. Update the cache only when your content changes.

[GiorgosK]

The best thing for your blog is a file cache, not any of these things. If it's so popular you really need to reduce its load, then generate static versions of all the pages and serve those instead of building them on each request. Update the cache only when your content changes.

Thanks Dan, exactly what I was in need of, great advice ...

how do you suggest that we proceed with this ? is there a configuration on apache servers that does this automatically or is it usually a custom coded solution ? any pointers to a good tutorial ?

[Dan Grossman]

//check if the cache file already exists

//generate a unique filename based on the REQUEST_URI to
//implement this in a generic fashion

if (file_exists('cache.html')) {

  // the output is already cached, so just
  // dump the file's contents to the browser
  readfile('cache.html');

} else {

  // otherwise, the cache doesn't exist yet
  // so re-generate the content

  // turn on output buffering so your code's output
  // gets stored in the buffer instead of sent to the
  // browser
  ob_start();

  // here you can place the existing PHP and HTML
  // you want to cache

  // now, write the output you captured in the buffer
  // into the cache file
  $fp = fopen('cache.html', 'w'); 
  fwrite($fp, ob_get_contents());
  fclose($fp);

  // and output the buffer's contents to the
  // browser as well
  ob_end_flush();

} 

If you have header and footer or some other template system already, then you could have this implemented across the entire site in minutes.

There's probably a WordPress plugin for caching somewhere if that's what you're using... I'm not the type to go look, though. There are a couple pieces of my blog template that are separately cached to files and update when the cache is 5 minutes old (checking filemtime compared to current time)... just quickly coded into the theme.

[GiorgosK]

Dan thanks a lot for the code, I am going to try it out ...