Php Memcache Design Patterns issue - php

Question

For a small home project I am working on I have been looking for OO design patterns for Memcache implementation, but so far haven't found something I feel fits, so maybe my approach is wrong.
I have a DB connection class and an baseModel class so I want to implement caching on the baseModel where appropriate.
I have implemented the Database connection and the Cacher as Singlton patterns.
I cannot seem to get the Cacher class to read the data or trigger the echo "<p>Getting from cache"; line after I refresh the page on the base Model "loadFromDb" function
Here are the classes:
class Cacher {
protected static $cacher = null;
private static $settings;
public static function getCache() {
if (self::$cacher != null) {
return self::$cacher;
}
try {
self::$settings = parse_ini_file("./configs/main.ini");
self::$cacher = new Memcache();
self::$cacher->connect(
self::$settings['cache_server_host']
, self::$settings['cache_server_port']
);
} catch (Exception $e) {
// TODO log error and mitigate..
echo "Error connecting memcache";
die();
}
var_dump(self::$cacher->getstats());
return self::$cacher;
}
public static function getData($key) {
if (self::$cacher == null) {
self::getCache();
}
return self::$cacher->get($key);
}
public static function setData($key, $data, $expire = 0) {
if (self::$cacher == null) {
self::getCache();
}
if (self::$cacher)
return self::$cacher->set($key, $data, MEMCACHE_COMPRESSED, $expire);
}
}
class ModelBase {
protected $fields = array();
protected $class = null;
function __construct($class_name) {
$this->class = $class_name;
$this->fields = Database::getFields($class_name);
}
public function loadFromDB($id, $fromCache = true) {
$key = "loadFromDB_{$this->class}_{$id}";
if ($fromCache) {
$data = Cacher::getData($key);
if ($data) {
echo "<p>Getting from cache";
return unserialize($data);
} else {
echo "<p>No cache data. going to DB";
}
}
$values = Database::loadByID($this->class, $this->fields[0], $id);
foreach ($values as $key => $val) {
$this->$key = $val;
}
$dataSet = Cacher::setData($key, serialize($this));
echo "<p>Data set = $dataSet";
}
}
Memcache service is running and I can read data directly back if I read the cache directly after I write it, but what I want is to read the data from the DB only the first time the page loads, after that use the cache....
Any comments welcome...

Answer 1

Try doing it like (let the result of the cache decide if you should query the db):
<?php
public function loadFromDB($id) {
$key = "loadFromDB_{$this->class}_{$id}";
//query cache
$data = Cacher::getData($key);
//is it found
if (!empty($data)) {
//echo "<p>Getting from cache";
return unserialize($data);
}
//no so lest query db
else {
//echo "<p>No cache data. going to DB";
$values = Database::loadByID($this->class, $this->fields[0], $id);
foreach ($values as $key => $val) {
$this->$key = $val;
}
//store it in cache
//$dataSet = Cacher::setData($key, serialize($this));
$dataSet = Cacher::setData($key, serialize($values));//<<store the db result not the class
}
//echo "<p>Data set = $dataSet";
return unserialize($dataSet);
}
?>