PHP一个小巧的缓存类

功能很简单，就是缓存整个页面，可以设定缓存时间，可以缓存特定的URL，例如：test.php?id=12，当目标文件更新时，如test.php，缓存文件也会更新，即使仍处于缓存期内。

class cache
{
var $cache_dir = './cache/';//This is the directory where the cache files will be stored;
var $cache_time = 120;//How much time will keep the cache files in seconds.

var $caching = false;
var $file = '';

function cache()
{
//Constructor of the class
$this->file = $this->cache_dir . urlencode( $_SERVER['REQUEST_URI'] );
if(file_exists($this->file)) $expired = $this->check_expire();
else $expired = false;
if ( file_exists ( $this->file ) && ( filemtime ( $this->file ) + $this->cache_time ) > time() && !$expired )
{
//Grab the cache:
$handle = fopen( $this->file , "r");
do {
$data = fread($handle, 8192);
if (strlen($data) == 0) {
break;
}
echo $data;
} while (true);
fclose($handle);
exit();
}
else
{
//create cache :
$this->caching = true;
ob_start();
$now = time();
echo "<!--last modified:".$now."-->\n";
}
}

function close()
{
//You should have this at the end of each page
if ( $this->caching )
{
//You were caching the contents so display them, and write the cache file
$data = ob_get_clean();
echo $data;
$fp = fopen( $this->file , 'w' );
fwrite ( $fp , $data );
fclose ( $fp );
}
}
function check_expire(){
$fp = fopen($this->file,"r");
preg_match("/\:([\d]+)\-/",fread($fp,200),$time);
$modify_time = $time[1];
if($modify_time<filemtime($_SERVER['SCRIPT_FILENAME'])){
return true;
}
else{
return false;
}