image caching

so while i was making that aep thing, i had to think of a quick way to cache images. the aep script takes a little bit to pull data about a user and generate and image, so i wanted to minimize the number of times that is done. my first attempt was to do it strictly with php. i think it was a pretty good solution:

function dump_png($f){
  $fp = fopen($f, "rb");

header("Content-Type: image/png");

$user = isset($_GET['u']) ? $_GET['u'] : 'urble';
$cachefile = "cache/$user.png";

# check cache
if( file_exists($cachefile) ){
  $lt = strtotime('-1 day');
  $ft = filemtime($cachefile);

  if( $ft > $lt )

make_png(compute_aep($user), $cachefile);

but i wanted to nginx to cache things since i figure they do it better than me. so i just grabbed a few settings that probably could be better optimized, but i like how they work so far.

# added these two lines
fastcgi_cache_path /tmp/cache levels=1:2 keys_zone=AEPIMGS:10m inactive=1d;
fastcgi_cache_key "$scheme$request_method$host$request_uri";

server {

    # ...stuff...

    location ~ \.php$ {
        include        fastcgi_params;
        fastcgi_index  index.php;
        fastcgi_param  SCRIPT_FILENAME  $document_root$fastcgi_script_name;

        # and added these lines
        fastcgi_cache AEPIMGS;
        fastcgi_cache_valid 1d;

but i probably don't know what i'm doing.