As we know, the database will use many resource and time to query the information of Image. If we want to save time, we could do optimization with cache the result. What I use is two functions, you could use other PHP cache library too. The code I use is version 1.13. !! Please note: because I don't open the comment function, so it may have problem with comment.

You could go to site http://henku.info to see the cache result.

1, Edit the functions-db.php under zp-core directory.

2, Search function query_single_row, change it to:

function query_single_row($sql)
{
if ($cache = get_cache($sql))
return $cache;

$result = query($sql);
if ($result) {
$singlerow = mysql_fetch_assoc($result);

store_cache($sql, $singlerow);
return $singlerow;

} else {
return false;
}
}

3, Search function query_full_array, change it to:

function query_full_array($sql)
{
if ($cache = get_cache($sql))
return $cache;

$result = query($sql);
if ($result) {
$allrows = array();
while ($row = mysql_fetch_assoc($result))
$allrows[] = $row;

store_cache($sql, $allrows);
return $allrows;

} else {
return false;
}
}

4, Last thing, add two functions in functions-db.php. You could change "cachedirectory" to your cache directory, and change $cache_time_out to the expire time you want. 30 24 3600 is 30 days.

function store_cache($query, $result_cache)
{
if (preg_match("/^(insert|delete|update|replace)\s+/i",$query))
return;
if (stristr($query, "ORDER BY RAND"))
return;

$cache_file = 'cachedirectory/'. md5($query);
error_log (serialize($result_cache), 3, $cache_file);

}

function get_cache($query)
{
$cache_time_out = 30 24 3600;

if (preg_match("/^(insert|delete|update|replace)\s+/i",$query))
    return;
if (stristr($query, "ORDER BY RAND"))
    return;

$cache_file = 'cachedirectory/'. md5($query);
if ( file_exists($cache_file) )
{
    if ( (time() - filemtime($cache_file)) > $cache_time_out )
    {
        unlink($cache_file);
    }
    else
    {
        $result_cache = unserialize(file_get_contents($cache_file));
        return $result_cache;
    }
}

}

The normal albums and images data is cached. The other searches are not frequent enough to warrant caching.