LFU算法的PHP实现

/**
 * LFU是最近最不常用页面置换算法(Least Frequently Used),也就是淘汰一定时期内被访问次数最少的页
 */
class LFU_Cache{
    private $array_lfu = array();
    private $array_count = array();
    private $max_size = 0;

    function __construct($size)
    {
        // 缓存最大存储
        $this->max_size = $size;
    }

    public function set_value($key, $value)
    {
        // 如果存在，则存入值
        if (array_key_exists($key, $this->array_lfu)) {
            $this->array_lfu[$key] = $value;
        }else if(count($this->array_lfu) < $this->max_size){
            $this->array_lfu[$key] = $value;
        }else{
            // 找出最少使用的key，删除它
            $min_key = '';
            $min_count = PHP_INT_MAX;
            foreach($this->array_count as $key=>$value){
                if($value < $min_count){
                    $min_key = $key;
                    $min_count = $value;
                }
            }

            unset($this->array_lfu[$min_key]);
            unset($this->array_count[$min_key]);
        }

        // 次数加一
        if (array_key_exists($key, $this->array_count)) {
            $this->array_count[$key] = $this->array_count[$key] + 1;
        }else{
            $this->array_count[$key] = 1;
        }
        
    }

    public function get_value($key)
    {
        $ret_value = false;

        if (array_key_exists($key, $this->array_lfu)) {
            $ret_value = $this->array_lfu[$key];
            $this->array_count[$key] = $this->array_count[$key] + 1;
        }
        return $ret_value;
    }

    public function vardump_cache()
    {
        var_dump($this->array_lfu);
    }
}

$cache = new LFU_Cache(5);
$cache->set_value("01", "01");
$cache->get_value('01');
$cache->set_value("02", "02");
$cache->set_value("03", "03");
$cache->set_value("04", "04");
$cache->set_value("05", "05");
$cache->set_value("03", "33");
$cache->vardump_cache();

$cache->set_value("06", "06");
$cache->set_value("07", "07");
$cache->vardump_cache();