printLog.php

function formatMicrotime($time, $format = null){
  if (is_null($format)) {
    $formated = sprintf('%0.5f', $time);
  } else {
    $sec = (int)$time;
    $msec = (int)(($time - $sec) * 100000);
    $formated = date($format, $sec) . '.' . $msec;
  }
  return $formated;
}

function printLog($message, $echo = false, $startTime = null, $endTime = null) {
  if (is_null($startTime)) {
    $startTime = $GLOBALS['gStartTime'];
  }
  if (is_null($endTime)) {
    $endTime = microtime(true);
  }

  $formatedTime = formatMicrotime($endTime, 'Y-m-d H:i:s');
  $elapseTime = $endTime - $GLOBALS['gLapStartTime'];
  $elapseTime = formatMicrotime($elapseTime);
  $msg = $formatedTime . "\t" . $elapseTime . "\t" . $message . "\n";
  if ($echo) {
    print $msg;
  }
  error_log($msg, 3, "process_log.txt");
  
  $GLOBALS['gLapStartTime'] = $endTime;
}