264 lines
6.6 KiB
PHP
264 lines
6.6 KiB
PHP
<?php
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/**
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* DNS Library for handling lookups and updates.
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*
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* Copyright (c) 2020, Mike Pultz <mike@mikepultz.com>. All rights reserved.
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*
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* See LICENSE for more details.
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*
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* @category Networking
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* @package Net_DNS2
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* @author Mike Pultz <mike@mikepultz.com>
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* @copyright 2020 Mike Pultz <mike@mikepultz.com>
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* @license http://www.opensource.org/licenses/bsd-license.php BSD License
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* @link https://netdns2.com/
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* @since File available since Release 1.1.0
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*
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*/
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/**
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* A class to provide simple dns lookup caching.
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*
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*/
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class Net_DNS2_Cache
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{
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/*
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* the filename of the cache file
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*/
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protected $cache_file = '';
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/*
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* the local data store for the cache
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*/
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protected $cache_data = [];
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/*
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* the size of the cache to use
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*/
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protected $cache_size = 0;
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/*
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* the cache serializer
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*/
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protected $cache_serializer;
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/*
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* an internal flag to make sure we don't load the cache content more
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* than once per instance.
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*/
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protected $cache_opened = false;
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/**
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* returns true/false if the provided key is defined in the cache
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*
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* @param string $key the key to lookup in the local cache
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*
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* @return boolean
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* @access public
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*
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*/
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public function has($key)
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{
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return isset($this->cache_data[$key]);
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}
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/**
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* returns the value for the given key
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*
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* @param string $key the key to lookup in the local cache
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*
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* @return mixed returns the cache data on sucess, false on error
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* @access public
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*
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*/
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public function get($key)
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{
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if (isset($this->cache_data[$key])) {
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if ($this->cache_serializer == 'json') {
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return json_decode($this->cache_data[$key]['object']);
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} else {
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return unserialize($this->cache_data[$key]['object']);
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}
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} else {
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return false;
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}
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}
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/**
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* adds a new key/value pair to the cache
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*
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* @param string $key the key for the new cache entry
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* @param mixed $data the data to store in cache
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*
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* @return void
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* @access public
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*
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*/
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public function put($key, $data)
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{
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$ttl = 86400 * 365;
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//
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// clear the rdata values
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//
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$data->rdata = '';
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$data->rdlength = 0;
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//
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// find the lowest TTL, and use that as the TTL for the whole cached
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// object. The downside to using one TTL for the whole object, is that
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// we'll invalidate entries before they actuall expire, causing a
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// real lookup to happen.
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//
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// The upside is that we don't need to require() each RR type in the
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// cache, so we can look at their individual TTL's on each run- we only
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// unserialize the actual RR object when it's get() from the cache.
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//
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foreach ($data->answer as $index => $rr) {
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if ($rr->ttl < $ttl) {
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$ttl = $rr->ttl;
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}
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$rr->rdata = '';
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$rr->rdlength = 0;
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}
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foreach ($data->authority as $index => $rr) {
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if ($rr->ttl < $ttl) {
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$ttl = $rr->ttl;
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}
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$rr->rdata = '';
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$rr->rdlength = 0;
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}
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foreach ($data->additional as $index => $rr) {
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if ($rr->ttl < $ttl) {
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$ttl = $rr->ttl;
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}
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$rr->rdata = '';
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$rr->rdlength = 0;
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}
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$this->cache_data[$key] = [
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'cache_date' => time(),
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'ttl' => $ttl
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];
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if ($this->cache_serializer == 'json') {
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$this->cache_data[$key]['object'] = json_encode($data);
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} else {
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$this->cache_data[$key]['object'] = serialize($data);
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}
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}
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/**
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* runs a clean up process on the cache data
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*
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* @return void
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* @access protected
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*
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*/
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protected function clean()
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{
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if (count($this->cache_data) > 0) {
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//
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// go through each entry and adjust their TTL, and remove entries that
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// have expired
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//
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$now = time();
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foreach ($this->cache_data as $key => $data) {
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$diff = $now - $data['cache_date'];
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if ($data['ttl'] <= $diff) {
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unset($this->cache_data[$key]);
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} else {
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$this->cache_data[$key]['ttl'] -= $diff;
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$this->cache_data[$key]['cache_date'] = $now;
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}
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}
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}
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}
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/**
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* runs a clean up process on the cache data
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*
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* @return mixed
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* @access protected
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*
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*/
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protected function resize()
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{
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if (count($this->cache_data) > 0) {
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//
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// serialize the cache data
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//
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if ($this->cache_serializer == 'json') {
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$cache = json_encode($this->cache_data);
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} else {
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$cache = serialize($this->cache_data);
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}
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//
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// only do this part if the size allocated to the cache storage
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// is smaller than the actual cache data
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//
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if (strlen($cache) > $this->cache_size) {
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while (strlen($cache) > $this->cache_size) {
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//
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// go through the data, and remove the entries closed to
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// their expiration date.
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//
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$smallest_ttl = time();
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$smallest_key = null;
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foreach ($this->cache_data as $key => $data) {
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if ($data['ttl'] < $smallest_ttl) {
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$smallest_ttl = $data['ttl'];
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$smallest_key = $key;
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}
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}
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//
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// unset the key with the smallest TTL
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//
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unset($this->cache_data[$smallest_key]);
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//
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// re-serialize
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//
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if ($this->cache_serializer == 'json') {
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$cache = json_encode($this->cache_data);
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} else {
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$cache = serialize($this->cache_data);
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}
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}
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}
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if ( ($cache == 'a:0:{}') || ($cache == '{}') ) {
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return null;
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} else {
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return $cache;
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}
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}
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return null;
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}
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}
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