php中使用文件缓存的例子

在web开发中，可以通过文件缓存，大大缓解数据库的压力。 如下代码是php中使用文件缓存的例子。

CacheLayer.php

1. class CacheLayer{
2. protected $root = "";
3. protected $cache = "";
4. protected $key = "";
5. protected $life = 0;
6. public function __construct($key, $root = "/cachelayer"){
7. $this->root = $_SERVER["DOCUMENT_ROOT"].$root;
8. $this->key = $key;
9. }
10. public function expired($life_span){
11. $this->life = $life_span;
12. $file = $this->root."/".$this->key.".cachelayer";
13. if(is_file($file)){
14. $mtime = filemtime($file);
15. return (time() >= ($mtime + $this->life));
16. }else{
17. return true;
18. }
19. }
20. public function put($content){
21. $file = $this->root."/".$this->key.".cachelayer";
22. if(!is_dir(dirname($this->root))){
23. return false;
24. }
25. $this->delete();
26. $content = json_encode($content);
27. return (bool)file_put_contents($file, $content);
28. }
29. public function get(){
30. $file = $this->root."/".$this->key.".cachelayer";
31. if(is_file($file)){
32. return json_decode(file_get_contents($file), true);
33. }
34. return array();
35. }
36. public function delete(){
37. $file = $this->root."/".$this->key.".cachelayer";
38. if(is_file($file)){
39. unlink($file);
40. return true;
41. }
42. return false;
43. }
44. }

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example.php

1. // Load the cachelayer and the database connection (db connection is optional)
2. require_once "CacheLayer.php";
3. require_once "db_connection.php";
5. // Create a instance of the cachelayer
6. $cl_nav = new CacheLayer("navigation");
7. // Check to see if the cache is expired (60 * 10 = 10 minutes)
8. if($cl_nav->expired(60 * 10)){
9. echo "Cache doesn't exist or is expired. Rebuilding...
   ";
10. // if the cache is expired rebuild it
11. $result = mysql_query("select id, title from navigation");
12. $new_cache = array();
13. while($row = mysql_fetch_assoc($result)){
14. $new_cache[] = $row;
15. }
16. // Save the array into the cache
17. $cl_nav->put($new_cache);
18. }
19. echo "Loading from cache...
    ";
20. // Get the cache
21. $cache = $cl_nav->get();
23. // Display the cache
24. foreach($cache as $row){

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