Cache for your database queries

<?php

/**
 * @desc Class that implements the Cache functionality
 */
class Cache
{

    /**
     * Function read retrieves value from cache
     *
     * @param $fileName -
     *            name of the cache file
     *            Usage: Cache::read('fileName.extension')
     */
    function read ($fileName)
    {
        $fileName = '/path/to/cache/folder' . $fileName;
        if (file_exists($fileName)) {
            $handle = fopen($fileName, 'rb');
            $variable = fread($handle, filesize($fileName));
            fclose($handle);
            return unserialize($variable);
        } else {
            return null;
        }
    }

    /**
     * Function for writing key => value to cache
     *
     * @param $fileName -
     *            name of the cache file (key)
     * @param $variable -
     *            value
     *            Usage: Cache::write('fileName.extension', value)
     */
    function write ($fileName, $variable)
    {
        $fileName = '/path/to/cache/folder' . $fileName;
        $handle = fopen($fileName, 'a');
        fwrite($handle, serialize($variable));
        fclose($handle);
    }

    /**
     * Function for deleteing cache file
     *
     * @param $fileName -
     *            name of the cache file (key)
     *            Usage: Cache::delete('fileName.extension')
     */
    function delete ($fileName)
    {
        $fileName = '/path/to/cache/folder' . $fileName;
        @unlink($fileName);
    }
}

//
// :: Save above code as `cache.php`
//

//
// :: Here is how you can use this in your application
//

require_once ('cache.php');

// instantiate it
$cache = new Cache();

// let's check if some cache file exists
$data = $cache->read('test_17.tmp'); // 17 is id of the article, for example

// it doesn't exist, fetch data from database
if (empty($data)) {
    $sql = "SELECT image, user_id, content FROM table WHERE id = 17";

    $data = $db->select_list($sql); // just an example
    $cache->write('test_17.tmp', $data);
}

// then use the data as you would normally
foreach ($data as $row) {
    //
}

//
// This way you will gain some speed and your database server will thank you.
//
// But there is a catch! It is very, very important not to forget to clear
// this cache if something gets changed on that particular article.
// So do not forget to add this lines after your update the article:
//

// include the class
require_once ('cache.php');

// instantiate it
$cache = new Cache();

// updating the article example
$data = 'some array for updating';
$db->update_record('table', $data);

// delete the cached item
$cache->delete('test_17.tmp');

?>