高并发下PHP写文件日志丢失

php代码：

<?php
/**
 * Created by PhpStorm.
 * User: andyfeng
 * Date: 2015/6/24
 * Time: 13:31
 */
class LogFileUtil {

    public static $fileHandlerCache;
    private static $initFlag = false;
    private static $MAX_LOOP_COUNT = 3;

    private static function init() {
        self::$initFlag = true;
        register_shutdown_function(array("LogFileUtil", "shutdown_func"));
    }

    /**
     * 输出到文件日志
     * @param $filePath 文件路径
     * @param $msg  日志信息
     * @return int
     */
    public static function out($filePath, $msg) {
        if (!self::$initFlag) {
            self::init();
        }
        return self::internalOut($filePath, $msg);
    }

    /**
     * @param $filePath
     * @param $msg
     * @param $loop
     * @return int
     */
    private static function internalOut($filePath, $msg, $loop = 0) {
        //以防一直添加失败造成死循环
        if ($loop > self::$MAX_LOOP_COUNT) {
            $result = 0;
        } else {
            $loop++;
            $fp = self::$fileHandlerCache["$filePath"];
            if (empty($fp)) {
                $fp = fopen($filePath, "a+");
                self::$fileHandlerCache[$filePath] = $fp;
            }
            if (flock($fp, LOCK_EX)) {
                $result = fwrite($fp, $msg);
                flock($fp, LOCK_UN);
            } else {
                $result = self::internalOut($filePath, $msg, $loop);
            }
        }
        return $result;
    }

    function shutdown_func() {
        if (!empty(LogFileUtil::$fileHandlerCache)) {
            if (is_array(LogFileUtil::$fileHandlerCache)) {
                foreach (LogFileUtil::$fileHandlerCache as $k => $v) {
                    if (is_resource($v))
                        //file_put_contents("close.txt",$k);
                        fclose($v);
                }
            }
        }
    }
}