it says
/**
* Reads the cache file and returns the content.
*
* @param string The file path
* @param mixed The type of data you want to be returned
* sfFileCache::READ_DATA: The cache content
* sfFileCache::READ_TIMEOUT: The timeout
*
* @return string The content of the cache file.
*
* @throws sfCacheException
*/
but has to be
/**
* Reads the cache file and returns the content.
*
* @param string The file path
* @param mixed The type of data you want to be returned
* sfFileCache::READ_DATA: The cache content
* sfFileCache::READ_TIMEOUT: The timeout
* sfFileCache::READ_LAST_MODIFIED: The last modification timestamp
*
* @return string The content of the cache file.
*
* @throws sfCacheException
*/
Flag READ_LAST_MODIFIED is missing..