CachedMySQLDatabase - stores results of SELECT queries as arrays and reuses those... not sure if this is a good idea, though

CachedMySQLDatabase.php

<?php

/**
 * Class CachedMySQLDatabase
 * @inheritdoc
 */
class CachedMySQLDatabase extends MySQLDatabase
{

    protected $cache = array();

    public function query($sql, $errorLevel = E_USER_ERROR)
    {
        $method   = strtolower(substr($sql, 0, strpos($sql, ' ')));
        $cacheKey = crc32($sql);

        //skip anything but select queries
        if ($method !== "select") {
            return parent::query($sql, $errorLevel = E_USER_ERROR);
        }

        if (!isset($this->cache[$cacheKey])) {
            //create array data set from result
            $handle = $this->dbConn->query($sql);
            if (!$handle && $errorLevel) {
                $this->databaseError("Couldn't run query: $sql | " . $this->dbConn->error, $errorLevel);
            }
            $dataset = array();
            while ($data = $handle->fetch_assoc()) {
                $dataset[] = $data;
            }
            $handle->free();
            $this->cache[$cacheKey] = $dataset;
        }

        if (!isset($dataset)) {
            $dataset = $this->cache[$cacheKey];
        }

        return new CachedMySQLQuery($this, $dataset);

    }

}

CachedMySQLQuery.php

<?php

/**
 * A result-set from a MySQL database.
 *
 * @package framework
 * @subpackage model
 */
class CachedMySQLQuery extends SS_Query
{

    /**
     * The MySQLDatabase object that created this result set.
     * @var MySQLDatabase
     */
    protected $database;

    /**
     * The internal MySQL handle that points to the result set.
     * @var resource
     */
    protected $arrayObject;

    /**
     * @var int
     */
    protected $iterator = 0;

    /**
     * Hook the result-set given into a Query class, suitable for use by
     * SilverStripe.
     *
     * @param SS_Database $database The database object that created this query.
     * @param array $arrayObject the internal mysql handle that is points to the resultset.
     */
    public function __construct(MySQLDatabase $database, array $arrayObject)
    {
        $this->database    = $database;
        $this->arrayObject = $arrayObject;
    }

    public function __destruct()
    {
    }

    /**
     * {@inheritdoc}
     */
    public function seek($row)
    {
        $this->iterator = $row;

        return isset($this->arrayObject[$this->iterator]) ? $this->arrayObject[$this->iterator] : false;
    }

    /**
     * {@inheritdoc}
     */
    public function numRecords()
    {
        return count($this->arrayObject);
    }

    /**
     * {@inheritdoc}
     */
    public function nextRecord()
    {

        $row = isset($this->arrayObject[$this->iterator]) ? $this->arrayObject[$this->iterator] : false;
        $this->iterator++;

        return $row;
    }
}