Plugin a specific cache functionality?

Question

I have written a plugin that puts a (google) favicon in front of each link in my blog. Really simple. Just uses a simple preg_replace_callback on hrefs:

$changed_html_reference = preg_replace_callback(self::HTML_REF_REGEX, 
   array($this,'AddExtraHtmlToOneHref'), $strHtmlBodyText);

with a

add_filter('the_content', array($this,'ReplaceAll'), 9);

for the replacement and a default call to the google site for the icon (snip out of class) :

const GOOGLE_ICON_URL = 'http://www.google.com/s2/favicons?domain=';
function HttpDownloadFeed()
{
 $parsed_url = parse_url($this->url);  
 $data_r = wp_remote_get(self::GOOGLE_ICON_URL . $parsed_url['host']);
 $data = $data_r['body'];
 return $data;
}

I now have taken the approach of making my own cache class which stores the icons in directories like e.g. /cache/com/facebook/www/f.png.

But I am now thinking about the location of that class. For easiness i placed the cache in the wp-content directory. The following questions I have:

• could i plugin an existing cache / cache plugin to do the caching for me?
• what is the best location for my own cache thing? should i put it under /wp-content/cache or /plugins/myplugin/mycache or even /themes/mytheme/cache ?

or is there even a better approach to this?

(I am using the com/facebook/www approach because i also store session date of stumbleupon, delicious etc...in there and i only want to call these pages/feeds once incl. the request for a google favicon) (and since i need to display the icon and not all browser support inline displaying of icons embedded in html i need to write them to a directory available to the client).

Answer 1

Most of WordPress caching functionality is set up with text (serialized if needed) in mind. Since you need to store binary data it is probably better to maintain own cache.

As for location of cache I think it depends:

• for single personal installation I would pick directory that is short and makes nice URL, for example I store icons at /images/icons/ (/images/ being my directory for all images)
• for something that might be used across different installations or by other users I think /plugins/myplugin/mycache/ makes most sense if functionality is packaged as plugin (same but in theme directory, if part of theme)

Answer 2

Could i plugin an existing cache / cache plugin to do the caching for me?

Yes, you could but the question is if that makes sense. The file-system is a pretty good database for image-files.

What is the best location for my own cache thing? should I put it under /wp-content/cache or /plugins/myplugin/mycache or even /themes/mytheme/cache ?or is there even a better approach to this?

It always depends a simple place is a subfolder in the uploads folder as that one is often write-able.