Caching Database Data

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1Introduction

This mini-tutorial aims to cache data retrieved from a database.

We'll assume that you already have a website based on Temma, with a controller that displays data from a relational database.

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2Configuration

In the configuration file, we'll add a data source corresponding to a Memcache server.

Edit the etc/temma.php file:

<?php

return [
    'application' => [
        'dataSources' => [
            'db'    => 'mysql://user:pwd@localhost/base',
            'cache' => 'memcache://localhost',
        ],
    ],
];

• Line 6: Defines the data source connected to a MySQL database.
• Line 7: Defines the data source connected to a Memcache server.

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3Controller

Let’s imagine a very simple controller that displays a list of users.
Here’s an example implementation:

<?php

/** User controller. */
class User extends \Temma\Web\Controller {
    /** Action that displays the list of users. */
    public function list() {
        // fetch the list from the database
        $users = $this->_loader->UserDao->search();
        // store the list in a template variable
        $this['users'] = $users;
    }
}

Each time the list action is accessed, a query is executed on the database via the UserDao object.

Now let's see how we can add caching to avoid querying the database every time:

<?php

/** User controller. */
class User extends \Temma\Web\Controller {
    /** Action that displays the list of users. */
    public function list() {
        // define the cache key
        $cacheVarName = 'user:list';
        // fetch the list from the cache
        $users = $this->cache->get($cacheVarName, function() {
            // this code runs if the value is not cached
            // fetch the list from the database
            return $this->_loader->UserDao->search();
        });
        // store the list in a template variable
        $this['users'] = $users;
    }
}

All related information is available in the cache documentation.