Description:
------------
get_defined_functions has 1 optinal parameter.
ReflectionFunction instead reports it as mandatory.

https://3v4l.org/pRaFj

Bug present since 7.1.10

Possible commit that introduced the bug:
https://github.com/php/php-src/commit/58aa726548b18c4a48dd9804063b4eb8845aa7ef

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

$refFunc = new \ReflectionFunction('get_defined_functions');
var_dump($refFunc->getNumberOfRequiredParameters());
foreach ($refFunc->getParameters() as $parameter) {
    var_dump(sprintf('Parameter: "%s"; optional: %s', $parameter->name, var_export($parameter->isOptional(), true)));
}


Expected result:
----------------
int(0)
string(46) "Parameter: "exclude_disabled"; optional: true"

Actual result:
--------------
int(1)
string(46) "Parameter: "exclude_disabled"; optional: false"