How do I reboot ubuntu 16.04 remotely?

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Linux

PHP

Ubuntu

SSH

Hi,
I try to reboot my Ubuntu 16.04 through PHP.
I installed SSH2 extension, write code and it have a problem:

SSH connection: [OK]
Athentication: [OK]
Shell: [OK]
reboot -i
Welcome to Ubuntu 16.04 LTS (GNU/Linux 4.4.0-66-generic x86_64)

* Documentation: https://help.ubuntu.com/

332 packages can be updated.
4 updates are security updates.

Last login: Sun Mar 12 18:50:57 2017 from 192.168.80.137
]0;lam@lam: ~lam@lam:~$ reboot 
Failed to set wall message, ignoring: Interactive authentication required.
Failed to reboot system via logind: Interactive authentication required.
Failed to start reboot.target: Interactive authentication required.
See system logs and 'systemctl status reboot.target' for details.
Failed to open /dev/initctl: Permission denied
Failed to talk to init daemon. 

Then I use command line:

#chmod 777 /dev/initctl

It's work, Ubuntu reboot through PHP!!!!.
But after reboot, I try php code I gain, I show similar error above. I must #chmod 777 /dev/initctl again to keep it's work.
Please help me.
P/s: here my php code

<?php
        echo "SSH connection: ";
        if (!($resource=@ssh2_connect("192.168.80.137"))) {
                echo "[FAILED]<br />";
                exit(1);
        }
        echo "[OK]<br />";

        echo "Athentication: ";
        if (!@ssh2_auth_password($resource,"lam","root")) {
                echo "[FAILED]<br />";
                exit(1);
        }
        echo "[OK]<br />";

        echo "Shell: ";
        if (!($stdio = @ssh2_shell($resource,"xterm"))) {
                echo "[FAILED]<br />";
                exit(1);
        }
        echo "[OK]<br />";
		//$permission = "chmod 777 /dev/initctl \n";
		//fwrite($stdio,$permission);
        $command = "reboot\n";
        fwrite($stdio,$command);

        sleep(1);

        while($line = fgets($stdio)) {
                flush();
                echo $line."<br />";
        }

        fclose($stdio);
?>

What I have tried:

Reboot my Ubuntu 16.04 through PHP.