CACHE for LRU algorithm implemented by PHP

LRU is short for LastRecentUsed. it is used as a cache algorithm to invalidate the cache that is rarely used recently. Memcache uses this algorithm. The following uses a PHP implementation method. This algorithm puts each added content on the top of the cache to clear the content at the bottom of the cache when the cache is reached. You can use the following PHP code

LRU is short for Last Recent Used. it is Used as a cache algorithm to invalidate the cache that is rarely Used recently. Memcache uses this algorithm. The following uses a PHP implementation method. This algorithm puts each added content on the top of the cache to clear the content at the bottom of the cache when the cache is reached. The following PHP code can be used for simulation.

 capacity = $capacity;        $this->hashmap = array();        $this->head = new Node(null, null);        $this->tail = new Node(null, null);        $this->head->setNext($this->tail);        $this->tail->setPrevious($this->head);    }    public function get($key) {        if (!isset($this->hashmap[$key])) { return null; }        $node = $this->hashmap[$key];        if (count($this->hashmap) == 1) { return $node->getData(); }        // refresh the access        $this->detach($node);        $this->attach($this->head, $node);        return $node->getData();    }    public function put($key, $data) {        if ($this->capacity <= 0) { return false; }        if (isset($this->hashmap[$key]) && !empty($this->hashmap[$key])) {            $node = $this->hashmap[$key];            // update data            $this->detach($node);            $this->attach($this->head, $node);            $node->setData($data);        }        else {            $node = new Node($key, $data);            $this->hashmap[$key] = $node;            $this->attach($this->head, $node);            // check if cache is full            if (count($this->hashmap) > $this->capacity) {                // we're full, remove the tail                $nodeToRemove = $this->tail->getPrevious();                $this->detach($nodeToRemove);                unset($this->hashmap[$nodeToRemove->getKey()]);            }        }        return true;    }    private function attach($head, $node) {        $node->setPrevious($head);        $node->setNext($head->getNext());        $node->getNext()->setPrevious($node);        $node->getPrevious()->setNext($node);    }    private function detach($node) {        $node->getPrevious()->setNext($node->getNext());        $node->getNext()->setPrevious($node->getPrevious());    }}/** * Class that represents a node in a doubly linked list */class Node {    private $key;    // the content of the node    private $data;    // the next node    private $next;    // the previous node    private $previous;    public function __construct($key, $data) {        $this->key = $key;        $this->data = $data;    }    public function setData($data) {        $this->data = $data;    }    public function setNext($next) {        $this->next = $next;    }    public function setPrevious($previous) {        $this->previous = $previous;    }    public function getKey() {        return $this->key;    }    public function getData() {        return $this->data;    }    public function getNext() {        return $this->next;    }    public function getPrevious() {        return $this->previous;    }}