Description:
------------
It is possible to cause RTD key collisions through opcache. Here is a reproducer using file cache, though the same would also work through SHM:

file1.php:
<?php
return function() {};

file2.php:
<?php
$file = 'file1.php';
var_dump(include $file);
touch($file);
var_dump(include $file);

Then run file1.php first and file2.php second under -d opcache.file_cache_only=1.

Actual result:
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Fatal error: Runtime definition key collision for function {closure}. This is a bug