$out = `ls -la`;
echo '
'.$out.'';

输出结果：

total 10
drwxrwxrwx 1 root root 4096 Apr  7 15:42 .
drwxrwxrwx 1 root root 4096 Apr  7 14:48 ..
-rwxrwxrwx 1 root root  174 Apr  7 14:52 .buildpath
-rwxrwxrwx 1 root root  514 Apr  7 14:52 .project
drwxrwxrwx 1 root root    0 Apr  7 14:52 .settings
-rwxrwxrwx 1 root root  236 Apr  8 23:29 index.php

利用PHP的操作符 查询nginx 是否启动

$out = `ps -ef|grep nginx`;
echo '
'.$out.'';

root      2536     1  0 22:05 ?        00:00:00 nginx: master process nginx
www       2565  2536  0 22:08 ?        00:00:00 nginx: worker process
www       3312  2624  0 23:32 ?        00:00:00 sh -c ps -ef|grep nginx
www       3314  3312  0 23:32 ?        00:00:00 grep nginx

也就是说；php可以执行任何shell脚本!