Example of using file cache in php

In web development, file caching can be used to greatly alleviate the pressure on the database. The following code is an example of using file caching in php.

CacheLayer.php

class CacheLayer{
 protected $root = "";
 protected $cache = "";
 protected $key = "";
 protected $life = 0;
 public function __construct($key, $root = "/cachelayer"){
 $this->root = $_SERVER["DOCUMENT_ROOT"].$root;
 $this->key = $key;
 }
 public function expired($life_span){
 $this->life = $life_span;
 $file = $this->root."/".$this->key.".cachelayer";
 if(is_file ($file)){
 $mtime = filemtime($file);
 return (time() >= ($mtime + $this->life));
 }else{
 return true;
 }
 }
 public function put($content){
 $file = $this->root."/".$this->key.".cachelayer";
 if(!is_dir(dirname($this->root ))){
 return false;
 }
 $this->delete();
 $content = json_encode($content);
 return (bool)file_put_contents($file, $content);
 }
 public function get (){
 $file = $this->root."/".$this->key.".cachelayer";
 if(is_file($file)){
 return json_decode(file_get_contents($file), true);
 }
 return array();
 }
 public function delete(){
 $file = $this->root."/".$this->key.".cachelayer";
 if( is_file($file)){
 unlink($file);
 return true;
 }
 return false;
 }
}

example.php

// Load the cachelayer and the database connection (db connection is optional)
require_once "CacheLayer.php";
require_once "db_connection.php";

/ / Create a instance of the cachelayer
$cl_nav = new CacheLayer("navigation");
// Check to see if the cache is expired (60 * 10 = 10 minutes)
if($cl_nav->expired(60 * 10)){
 echo "Cache doesn't exist or is expired. Rebuilding...";
 // if the cache is expired rebuild it
 $result = mysql_query("select id, title from navigation");
 $new_cache = array();
 while($row = mysql_fetch_assoc($result)){
 $new_cache[] = $row;
 }
 // Save the array into the cache
 $cl_nav-> ;put($new_cache);
}
echo "Loading from cache...";
// Get the cache
$cache = $cl_nav->get();

// Display the cache
foreach($cache as $row){
 $id = $row["id"];
 $title = $row["title"];
 echo "$title";
}

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