file_get_contents无法打开流:没有这样的文件或目录

我收到一个相当奇怪的错误

file_get_contents('/var/www/site/config/../runtime/cookies/1a8dd816aafc1118dc5cbf7fd0263f20/cookie.txt'): failed to open stream: No such file or directory

所以我把代码改成：

if (file_exists($cookie_file)) {
    echo file_get_contents($cookie_file);
} else {
    echo "$cookie_file does not exist'n";
}

并输出：

/var/www/site/config/../runtime/cookies/1a8dd816aafc1118dc5cbf7fd0263f20/cookie.txt does not exist

在命令行中，如果我进行

cat /var/www/site/config/../runtime/cookies/1a8dd816aafc1118dc5cbf7fd0263f20/cookie.txt

它能很好地跟踪文件

权限也很好：

ls -lrt /var/www/site/config/../runtime/cookies/1a8dd816aafc1118dc5cbf7fd0263f20/cookie.txt
-rwxrwxrwx. 1 apache apache 391 Feb 11 16:27 /var/www/site/config/../runtime/cookies/1a8dd816aafc1118dc5cbf7fd0263f20/cookie.txt

所以，是的，我很困惑为什么它不会读取清楚存在的文件。

有什么想法吗？