cache identical queries

CachedMySQLDatabase.php

<?php

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

    protected $cache = array();

    public function query($sql, $errorLevel = E_USER_ERROR)
    {
        $cacheKey = crc32($sql);
        if (isset($this->cache[$cacheKey])) {
            return $this->cache[$cacheKey];
        }

        $res                    = parent::query($sql, $errorLevel = E_USER_ERROR);
        $this->cache[$cacheKey] = $res;

        return $res;
    }

}