A simple mcrypt example being set and retrieved in a cookie. For some reasion, in PHP 7, setcookie doesn't appear to set anything and $_COOKIE returns null

mcrypt-test.php

<?php 
$cookie_name = 'my_cookie';
$key = 'L+Hu+ ~bK$BUd;Jcc;M+/d7LP#qzU_i6P&Aq86Q/}=wYuUo:Q}@Y)(=d|y}+E5.oK)hgHH1R|/)v-zR-cp}E3|FdnY/&jd^&o/mKO&|Vhn2liz#PY~|^}6Zc:u? O^|p';
$secure = '0';
$session_id = 'ABCDEFGHIJKLMNOP';
$data = $session_id.'~~'.$secure;
$mode = MCRYPT_MODE_NOFB;
$cipher = MCRYPT_RIJNDAEL_128;
$key_size = mcrypt_get_key_size($cipher, $mode);
if (isset($key[$key_size])) {
    // Shorten the key to the maximum size
    $key = substr($key, 0, $key_size);
}
$iv_size = mcrypt_get_iv_size($cipher, $mode);
$iv = mcrypt_create_iv($iv_size, MCRYPT_DEV_URANDOM);
$data_encrypt = mcrypt_encrypt($cipher, $key, $data, $mode, $iv);
$data_encode = base64_encode($iv.$data_encrypt);
$stored = urlencode($data_encode);
$stored_correct = setcookie($cookie_name, $stored, 31536000, "/");
echo '<pre>';
    var_dump($data_encode);
    var_dump($stored);
    var_dump($stored_correct);
echo '</pre>';
$cookie = $_COOKIE[$cookie_name];
$unstore = urldecode($cookie);
$data_decode = base64_decode($unstore, true);
$iv_part = substr($data_decode, 0, $iv_size);
$data_part = substr($data_decode, $iv_size);
$data_decrypt = mcrypt_decrypt($cipher, $key, $data_part, $mode, $iv_part);
echo '<pre>';
    var_dump($cookie);
    var_dump($unstore);
    var_dump($data_decrypt);
echo '</pre>';