PHP文件缓存示例

简介

在php程序中，缓存可以存储到Redis或者Memcache中，如果没有这些条件，或者服务器内存非常有限怎么办？可以将缓存内容写入到硬盘，写入到文件系统中，也是一个思路。下面是示例代码：

代码

<?php
namespace common\library;

use Psr\SimpleCache\CacheInterface;

class FileCache implements CacheInterface
{
    protected $filename;

    protected $handle;

    protected $keys = [];

    protected $spaceSize;

    protected $startTimestamp;

    public function __construct($filename, $spaceSize = 1024)
    {
        $this->startTimestamp = time();
        $this->filename = $filename;
        $this->spaceSize = $spaceSize;

        !is_dir(dirname($this->filename)) && mkdir(dirname($this->filename), 0755, true);
        $this->handle = fopen($this->filename, 'w+');
    }

    public function __destruct()
    {
        fclose($this->handle);
        unlink($this->filename);
    }

    public function get($key, $default = null)
    {
        $key = substr(md5($key), 0, 20);

        if (!isset($this->keys[$key])) {
            return $default;
        }

        $item = $this->parseId($this->keys[$key]);

        if ($item[1] != 0 && (time() - $this->startTimestamp) > $item[1]) {
            return $default;
        }

        fseek($this->handle, $item[0] * $this->spaceSize);
        $value = fread($this->handle, $this->spaceSize);
        return unserialize(rtrim($value));
    }

    public function set($key, $value, $ttl = null)
    {
        $key = substr(md5($key), 0, 20);
        $value = serialize($value);

        if (strlen($value) > $this->spaceSize - 1) {
            throw new \RuntimeException('not enough space');
        }

        if (!is_null($ttl) && $ttl > 1048575) {
            throw new \RuntimeException('Ttl out of range');
        }

        $value = str_pad($value, $this->spaceSize - 1, " ") . "\n";

        if (isset($this->keys[$key])) {
            $item = $this->parseId($this->keys[$key]);
            $start = $item[0] * $this->spaceSize;
            $index = $item[0];

        } else {
            $count = count($this->keys);
            $start = $count * $this->spaceSize;
            $index = $count;
        }

        fseek($this->handle, $start, SEEK_SET);
        fwrite($this->handle, $value);
        fflush($this->handle);

        $this->keys[$key] = $this->getId($ttl ? (time() - $this->startTimestamp) + $ttl : 0, $index);
        return true;
    }

    public function delete($key)
    {
        $key = substr(md5($key), 0, 20);
        unset($this->keys[$key]);
        return true;
    }

    public function clear()
    {
        ftruncate($this->handle, 0);
        fflush($this->handle);
        return true;
    }

    public function getMultiple($keys, $default = null)
    {
        $values = [];

        foreach ($keys as $key) {
            $values[$key] = $this->get($key, $default);
        }

        return $values;
    }

    public function setMultiple($values, $ttl = null)
    {
        foreach ($values as $key => $value) {
            $this->set($key, $value, $ttl);
        }

        return true;
    }

    public function deleteMultiple($keys)
    {
        foreach ($keys as $key) {
            $this->delete($key);
        }

        return true;
    }

    public function has($key)
    {
        return isset($this->keys[md5($key)]);
    }

    protected function getId($time, $count)
    {
        return $time << 20 | $count;
    }

    protected function parseId($id)
    {
        $id = str_pad(decbin($id), 40, '0', STR_PAD_LEFT);
        return [bindec(substr($id, 21)), bindec(substr($id, 0, 20))];
    }
}