在PHP中解析缓存控制头

/**
 * Parse the cache-control string into a key value array.
 *
 * @param string $cache_control
 *   The cache-control string.
 *
 * @return array
 *   Returns a key value array.
 */
function parse_cache_control($cache_control) {
  $cache_control_array = explode(',', $cache_control);
  $cache_control_array = array_map('trim', $cache_control_array);
  $cache_control_parsed = array();
  foreach ($cache_control_array as $value) {
    if (strpos($value, '=') !== FALSE) {
      $temp = array();
      parse_str($value, $temp);
      $cache_control_parsed += $temp;
    }
    else {
      $cache_control_parsed[$value] = TRUE;
    }
  }
  return $cache_control_parsed;
}