缓存PHP内容的建议

Question

So my site is starting to use too much resources. the core of my site is a badly-coded plugin for vbulletin. Unfortunately it's not that easy to just switch, so I'll just have to try to rewrite some stuff, but most importantly: The main page where different parameters are attached to takes way too much processing power like ?image.php?id=1 and ?image.php?id=2.. and such.

Anyways, I need something that I can use to cache these pages in html for each id, they don't really change that often, only when comments are posted so it's useless to load them every time. I never worked with anything like this before so any tips, hints, software to use are very welcome

EDIT: Reason I'm asking is because my processor usage on my host is starting to reach high and if I get more visitors I might get suspended.

EDIT: I was thinking a system something like this: a database with every ?id in it and the date it was last modified (like comment added or something) if the date is older than the last cached version saved as html, load the html, else run the php script and generate a new cached html. I'm probably gonna have to make something like this myself I guess, just not too sure how to get started on something like that.

Answer 1

You could add these in image.php at the very top

header("Cache-Control: private, max-age=10800, pre-check=10800");
header("Pragma: private");
header("Expires: " . date(DATE_RFC822, strtotime("2 day")));

if (isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])) {

    header('Last-Modified: ' . $_SERVER['HTTP_IF_MODIFIED_SINCE'], true, 304);
    exit;
}

Answer 2

Where is your real issue now? The database calls or serving up static content?

Sounds to me like you should start off with a simple cache using local file system. Can you cache the pages that you mention being the slowest in their entirety? If so you could write your own simple cache code, just writing out the file to disk and loading it from there when it has not expired/been invalidated.

There are other things like APC, memcaced, which might help you too. Quick google search will give you the low down there.

Answer 3

You could implement the above code for client side caching, as for server side you could store the processed (if vbulletin does something to image / resizing / cropping etc. which causes high memory usage) images into files (in some cache dir) so PHP doesn't have to process them every time the script is called.

Algorithm itself should consist of hashing the $_GET params that are needed for vbulletin such as id=2 or width=250 , height=250

so code would looke something like...

$file = 'cache_dir/'.md5('file_cached_'.$_GET['id'].'_w'.$_GET['width'].'_h'.$_GET['height']).'.jpg';
if ( ! file_exists($file))
{

  $image = get_image_by_id($_GET['id']);

  // this is just example...
  $image_blob = vbulletin_heavy_image_processing($image);

  file_put_contents($file, $image_blob);
  echo $image_blob;
}
else 
{
  echo file_get_contents($file);
}