public function __construct() {

$this->_dir = dirname(__FILE__) . '/files/';

}

public function cacheData($key, $value = '', $cacheTime = 0) {

$filename = $this->_dir  . $key . self::EXT;

if($value !== '') { // 将value值写入缓存

if(is_null($value)) {

return @unlink($filename);

}

$dir = dirname($filename);

if(!is_dir($dir)) {

mkdir($dir, 0777);

}

$cacheTime = sprintf('%011d', $cacheTime);

return file_put_contents($filename,$cacheTime . json_encode($value));

}

if(!is_file($filename)) {

return FALSE;

} 

$contents = file_get_contents($filename);

$cacheTime = (int)substr($contents, 0 ,11);

$value = substr($contents, 11);

if($cacheTime !=0 && ($cacheTime + filemtime($filename) < time())) {

unlink($filename);

return FALSE;

}

return json_decode($value, true);

}