PHP疑难解答注意事项：未知：1。。。其中'；什么是未知标记？

我遇到一个PHP错误，需要帮助解决：

[Fri May 08 10:20:41.234655 2015][：error][pid 6969][client 207.183.229.82:3038]PHP通知：未知：1。h->opened_path=[null]h->filename=[/var/www/example.com/htdocs/wp admin/network/site new.php]\n在第0行的未知位置，请参考：

当我尝试添加新站点时，新安装的WordPress会出现这种情况

但未知的标记是什么？为什么未知？我查看了文件

wp admin/network/site new.php

的第0行，它只包含一个php标记的开头：

[Fri May 08 10:20:41.234655 2015] [:error] [pid 6969] [client 207.183.229.82:3038] PHP Notice:  Unknown: 1. h->opened_path=[null]  h->filename=[/var/www/example.com/htdocs/wp-admin/network/site-new.php]\n in Unknown on line 0, referer: http://example.com/wp-admin/network/site-new.php
[Fri May 08 10:20:41.234716 2015] [:error] [pid 6969] [client 207.183.229.82:3038] PHP Notice:  Unknown: apc_cache_find [1627723]\n in Unknown on line 0, referer: http://example.com/wp-admin/network/site-new.php
[Fri May 08 10:20:41.235364 2015] [:error] [pid 6969] [client 207.183.229.82:3038] PHP Notice:  Unknown: 2. h->opened_path=[/var/www/example.com/htdocs/wp-admin/network/site-new.php]  h->filename=[/var/www/example.com/htdocs/wp-admin/network/site-new.php]\n in Unknown on line 0, referer: http://example.com/wp-admin/network/site-new.php