Description:
------------
Several developers upgraded to the latest PHP 7.1.12, and PHP 7.2.0 releases in the last two days and all have encountered the following warning while trying to use our product:

Warning: Narrowing occurred during type inference. Please file a bug report on bugs.php.net

Our code base is very large so rather than try to share the file that generates the warning I produced a simplification of the code that causes the issue, and which can be used to reliably reproduce the issue.
Please see the provided test script code.

To reproduce this: 
* Place the test script into your web root
* Start watching the server logs or config php to display warnings etc
* Visit the script in your browser

We've tested on several versions of PHP and the following is our findings:

* OSX + PHP 7.2.0 === affected
* OSX + PHP 7.1.12 === affected
* OSX + PHP 7.1.12RC5 === fine
* OSX + PHP 7.1.11 === fine
* Ubuntu + PHP 7.2.0 === affected
* Ubuntu + PHP 7.1.12 === affected

Test script:
---------------
<?php

opcache_reset();

function test($capability) {
    $needed = [];
    $caps = (array)$capability;
    foreach ($caps as $cap) {
        if ($cap == 1) {
            unset($needed[$cap][1]);
        } else if (true) {
            $needed[$cap][1] = true;
        }
    }
}

Expected result:
----------------
Importantly no warnings.

Actual result:
--------------
Warning: Narrowing occurred during type inference. Please file a bug report on bugs.php.net in Unknown on line 0

The effect this has in our code base is that during execution the $needed array will magically become null *most* of the time.
Once in a while it will correctly

To see this effect change the test script as follows:
<code>
<?php
opcache_reset();

function test($capability) {
    $needed = [];
    $caps = (array)$capability;
    foreach ($caps as $cap) {
        if ($cap == 1) {
            unset($needed[$cap][1]);
        } else if (true) {
            $needed[$cap][1] = true;
        }
    }
    var_dump($needed);
}

$test = new stdClass();
$test->a = 1;
$test->b = 2;
test($test);
</code>

Now when you call it most of the time it will output the warning and null.
*Occasionally* you will not get the warning, and you will get:

"array(1) { [2]=> array(1) { [1]=> bool(true) } }"