(PECL pecl_http >= 0.1.0)
http_match_modified — Match last modification
$timestamp = -1
   [, bool $for_range = false
  ]] )Matches the given Unix timestamp against the clients If-Modified-Since resp. If-Unmodified-Since HTTP headers.
timestampUnix timestamp; current time, if omitted
for_range
       if set to TRUE, the header usually used to validate HTTP ranges will be checked
      
   Returns TRUE if timestamp represents an earlier date than the header, else FALSE.