Cached Dynamic Modules Page 5

Here we determine whether $buf can instead be built from the $cache_file by checking the following:

• if cache paramer is set and less than 10, we are forced to skip the cache!
• if cache file exists and the cache parameter is not set, check if default cache
  time has not yet expired, for then we can use the cache and we should not update it
• if cache file exists and cache parameter is set, check if that time has not yet
  expired, for then we can use the cache and we should not update it
• if we should not use the cache because it is expired, we’ll update it after we executed the module

Thus we can now make the $buf creation conditional to the $read_cache
variable, by replacing the line that says:

<?php $buf = $fun ($arglist); ?>

with the the following code:

<?php
if ($read_cache || (!strlen ($buf .= $fun ($arglist)))) {
    if ($f = fopen ($cache_file, "r")) {
        while ($str = fgets ($f, 4096)) {
            $buf .= $str;
        }
        fclose ($f);
    } else $buf .= "<!-- $tag: error - cache is empty //-->n";
}
?>

Note that the module can force the cache (e.g. when database is down) by returning an empty
string (risking the cache has not yet been written, but in any case it does not generate a database
error, but here an empty place in the page with an html comment).

The last step is see if we should also update the cache, by continuing to add the following code before return $buf:

<?php
if ($write_cache && ($f = fopen ($cache_file, "w"))) {
    fputs ($f, $buf);
    fclose ($f);
}
?>

v
Now the parser is done and you can start creating both the res/ and cache/ subdirectories and
fill res/ with modules xxx.php that each implements the function handle_xxx ($arglist).